Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-20 Thread James B. Byrne

On Thu, February 19, 2015 13:41, Chris Murphy wrote:

 Linux distros experience on this front is terrible. Why? Linux OS's

Because Linux-land is a bazaar and Apple-land is a cathedral.  You
cannot have consistency at the user level without stability at the OS
and application framework level. That is simply not going to happen
with FOSS.


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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-20 Thread James B. Byrne

On Thu, February 19, 2015 22:01, Dennis Jacobfeuerborn wrote:
 On 19.02.2015 19:41, Chris Murphy wrote:

 Linux with a thousand knobs is never going become popular. Instead
 somebody has to go and create an opinionated system where most knobs
 are removed and replaced by sane/good/useful defaults.

Gnome3?

DFCAR. . .



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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Chris Murphy
On Thu, Feb 19, 2015 at 12:06 AM, John R Pierce pie...@hogranch.com wrote:
 On 2/18/2015 9:39 PM, Chris Murphy wrote:

 You might be a candidate for LVM integrated raid. It uses the md
 kernel code on the backend, but it's all LVM tools to create, manage
 and monitor. The raid level is defined per LV, instead of all LV's in
 a VG inheriting the underlying raid. It supports all levels of raid
 including 5/6. ... ...
 ...
 ... ... btrfs ...


 actually, I prefer zfs.   I was just saying how I do it on CentOS, where zfs
 is not really an option.

It should be possible on CentOS 7, I know a couple people using ZoL in
production on Fedora since circa Fedora 19. The ZoL implementation is
not nearly as kernel version dependent as Btrfs is right now. But I
think most anyone would say at the moment the implementation is much
better on FreeBSD.

While ZFS is production stable, Btrfs comes with caveats. But already
it requires far less resources than ZFS, can grow and shrink in ways
ZFS can't, and I think snapshots are easier to understand, no
parent-child type relationship.


  but, is that lvm integrated raid stuff available in RHEL/CentOS 6 or 7
 yet ?

Yes since CentOS 6.3.


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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Kahlil Hodgson
On 20 February 2015 at 05:25, Chris Murphy li...@colorremedies.com wrote:
 I'd say your mom is an admin in the sense that chickens fly and horses swim.

 It's a confusing analogy. Chickens don't fly. Horses do swim.

I have a couple of chickens, and yes, the buggers do fly if you don't
clip their flight feathers. :-)
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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread m . roth
Kahlil Hodgson wrote:
 On 20 February 2015 at 05:25, Chris Murphy li...@colorremedies.com
 wrote:
 I'd say your mom is an admin in the sense that chickens fly and horses
 swim.

 It's a confusing analogy. Chickens don't fly. Horses do swim.

 I have a couple of chickens, and yes, the buggers do fly if you don't
 clip their flight feathers. :-)

I can't resist... tie your kangaroos, er, chickens down, sport,
tie your chickens down...

   mark old songs 'r' us

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Chris Murphy
On Thu, Feb 19, 2015 at 12:25 AM, Niki Kovacs i...@microlinux.fr wrote:

 A *user* never has to even see - or use - an installer. A USER has to USE a
 computer,  by which I mean the applications he or she needs to get some work
 done.

This is a false dichotomy. I reject it. There's too much fact to the
contrary. My mom has done an OS installation, she is most definitely
not an admin.


 The person who gets to be confronted by an OS installer is not a user, it's
 an ADMIN, which is an entirely different thing.

Well, you're wrong. I'd say you have never used a Windows or OS X
installer, they're a piece of cake. My house plant could do an
installation.

Anaconda isn't absurdly far behind that experience when it comes to
automatic installs (to blank drives).

An ADMIN should RTFM (a lot)
 and know his way about what you call esoteric things earlier in this
 thread (disks, partitions, volumes).

Sure. But GUI installers are general purpose tools for admins and user
use alike. If you care about things like partition tables and their
type codes, you aren't very well suited for using a GUI installer.


 My company (http://www.microlinux.fr) installs complete Linux-based networks
 for schools, town halls, public libraries etc. here in South France. For
 now, most of my server and desktop solutions are based on a highly modified
 version of Slackware Linux, with some CentOS and some RHEL here and there.
 I'm currently planning on migrating everything to CentOS in the long run.

 One of the founding principles of my company is the constant SEPARATION
 BETWEEN USING A COMPUTER AND ADMINISTRATING IT. A user never ever has to
 worry about things that pertain to system administration, and it would be
 very wrong if he or she ever has to deal with such a thing as an installer.
 For what it's worth, some of my users don't even know that this thing that
 they're using every day is called Linux under the hood. To them, it's just
 the machine that's running things like their library management software, or
 whatever.

It sounds like a mobile device running cyanogen, except there is no
clear line between user and administrating it.

I'm not a big fan of this separation between admin and computers when
it comes to basic plumbing type stuff like getting a working OS
installed. That should be something either really easy or totally
unnecessary like a stateless machine that can be reset and self heal.
The fact desktop haven't caught up to mobile in this regard, is sorta
embarassing.

Actually, Windows 8 comes fairly close to having statelessness, once
it's installed by a conventional installer. But not OS X. Notice how
Android, cyanogen don't even have monolithic installers. I'm just not
a fan of needing such a thing in the first place these days, it's
antiquated.



 So, as an admin, what I want from an installer is FLEXIBILITY... and not an
 assistant that reminds me of Microsoft Office's infamous Clippy and
 expects me to jump through burning loops to configure the system as I want
 it.

What you're describing is what kickstart is for. That's flexible and
fairly bug free. GUI installers, the more complex you make them
(flexibility) the buggier they are.

Fedora Atomic, one possible way of the future without any installer.
Atomic updates, and rollback and rollfoward.
http://www.projectatomic.io/

And another using btrfs send/receive images (not mentioned but could
instead use seed devices):
http://0pointer.net/blog/revisiting-how-we-put-together-linux-systems.html




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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Niki Kovacs

Le 19/02/2015 11:03, Chris Murphy a écrit :

This is a false dichotomy. I reject it. There's too much fact to the
contrary. My mom has done an OS installation, she is most definitely
not an admin.


I'd say your mom is an admin in the sense that chickens fly and horses swim.

:o)

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Dennis Jacobfeuerborn
On 19.02.2015 06:28, Chris Murphy wrote:
 On Wed, Feb 18, 2015 at 4:20 PM,  m.r...@5-cent.us wrote:
 Niki Kovacs wrote:
 Le 18/02/2015 23:12,
 
 close, but then, for mysterious reasons, Red Hat decided to cripple it
 into oblivion. Go figure.

 One word: desktop. That's what they want to conquer next.
 
 OK well there's a really long road to get to that pie in the sky. I
 don't see it happening because it seems there's no mandate to
 basically tell people what they can't have, instead it's well, we'll
 have a little of everything.
 
 Desktop OS that are the conquerers now? Their installers don't offer
 100's of layout choices. They offer 1-2, and they always work rock
 solid, no crashing, no user confusion, essentially zero bugs. The code
 is brain dead simple, and that results in stability.
 
 *shrug*
 
 Long road. Long long long. Tunnel. No light. The usability aspects are
 simply not taken seriously by the OS's as a whole. It's only taken
 seriously by DE's and they get loads of crap for every change they
 want to make. Until there's a willingness to look at 16 packages as a
 whole rather than 1 package at a time, desktop linux has no chance.
 The very basic aspects of how to partition, assemble, and boot and
 linux distro aren't even agreed upon. Fedora n+1 has problems
 installing after Fedora n. And it's practically a sport for each
 distro to step on an existing distros installer. This is
 technologically solved, just no one seems to care to actually
 implement something more polite.
 
 OS X? It partitions itself, formats a volume, sets the type code,
 writes some code into NVRAM, in order to make the reboot automatically
 boot the Windows installer from a USB stick. It goes out of it's way
 to invite the foreign OS.
 
 We can't even do that with the same distro, different version. It
 should be embarrassing but no one really cares enough to change it.
 It's thankless work in the realm of polish. But a huge amount of
 success for a desktop OS comes from polish.

I think the problem is that you simply have to draw a distinction
between technology and product.
The rise of the Linux desktop will never happen because Linux is not a
product but a technology and as a result has to be a jack of all trades.
The reason Apple is so successful I believe is because they understood
more than others that people don't care about technology but want one
specific consistent experience. They don't core how the harddisk is
partitioned.
So I can see the rise of the X desktop but only if X is willing to
have its own identity an eschew the desire to be compatible with
everything else or cater to both casual users and hard-core admin types.
In other words the X Desktop would have to be a very opinionated
product rather than a highly flexible technology.

 We also pretty much don't use any drives under 1TB. The upshot is we had
 custom scripts for  500GB, which made 4 partitions - /boot (1G, to fit
 with the preupgrade), swap (2G), / (497G - and we're considering
 downsizing that to 250G, or maybe 150G) and the rest in another partition
 for users' data and programs. The installer absolutely does *not* want to
 do what we want. We want swap - 2G - as the *second* partition. But if we
 use the installer, as soon as we create the third partition, of 497GB, for
 /, it immediately reorders them, so that / is second.
 
 I'm open to having my mind changed on this, but I'm not actually
 understanding why it needs to be in the 2nd slot, other than you want
 it there, which actually isn't a good enough reason. If there's a good
 reason for it to be in X slot always, for everyone, including
 anticipating future use, then that's a feature request and it ought to
 get fixed. But if it's a specific use case, well yeah you get to
 pre-partition and then install.
 

When I was younger I cared about where exactly each partition was
positioned but nowadays I refer to all my file systems using the uuid so
I don't really care anymore if / is the second or fifth partition. The
same is true for network interfaces. Since I mostly deal with physical
interfaces on Hypervisors only these days and there I am more interested
in bridges rather than the nics themselves I couldn't care less if the
interface is named eth0 or enp2something. I tend to think more in terms
of logical resources these days rather than physical ones.

Regards,
  Dennis
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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Chris Murphy
On Thu, Feb 19, 2015 at 3:28 AM, Niki Kovacs i...@microlinux.fr wrote:
 Le 19/02/2015 11:03, Chris Murphy a écrit :

 This is a false dichotomy. I reject it. There's too much fact to the
 contrary. My mom has done an OS installation, she is most definitely
 not an admin.


 I'd say your mom is an admin in the sense that chickens fly and horses swim.

It's a confusing analogy. Chickens don't fly. Horses do swim.


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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Chris Murphy
On Thu, Feb 19, 2015 at 5:47 AM, Dennis Jacobfeuerborn
denni...@conversis.de wrote:
 I think the problem is that you simply have to draw a distinction
 between technology and product.
 The rise of the Linux desktop will never happen because Linux is not a
 product but a technology and as a result has to be a jack of all trades.

I'm unconvinced. True, Chromebooks uses the linux kernel, and thus it
qualifies, sorta, as Linux desktop. But this is something analogous to
OS X using a FOSS kernel and some other BSD stuff, but the bulk of it
is proprietary. Maybe Chrome isn't quite that proprietary, but it's
not free either. And Chrome OS definitely is not jack of all trades.
What it can run is very narrow in scope right now.



 The reason Apple is so successful I believe is because they understood
 more than others that people don't care about technology but want one
 specific consistent experience. They don't core how the harddisk is
 partitioned.
 So I can see the rise of the X desktop but only if X is willing to
 have its own identity an eschew the desire to be compatible with
 everything else or cater to both casual users and hard-core admin types.
 In other words the X Desktop would have to be a very opinionated
 product rather than a highly flexible technology.

Hmm, well Apple as a pretty good understanding what details are and
aren't important to most people. That is, they discriminate. People do
care about technologies like disk encryption, but they don't care
about the details of how to enable or manage it. Hence we see both iOS
and Android enable it by default now. Change the screen lock password,
and it also changes the encryption unlock password *while removing*
the previous password all in one step. On all conventional Linux
distributions, this is beyond confusing and is totally sysadmin
territory. I'd call it a bad experience.

OK so that's mobile vs desktop, maybe not fair. However, OS X has one
button click full disk encryption as opt in post-install (and opt out
after). This is done with live conversion. The user can use the
computer normally while conversion occurs, they can put the system to
sleep, and even reboot it, and will resume conversion when the system
comes back up. Decrypt conversion works the same way. They are poised
to make full disk encryption a default behavior, without having
changed the user experience at all, in the next major release of the
software. I don't know whether they'll do it, but there are no
technical or usability impediments.

Linux distros experience on this front is terrible. Why? Linux OS's
don't have a good live conversion implementation (some people have
tried this and have hacks, but no distro has adopted this); but Ok the
installer could just enable it by default, obviating conversion. But
there's no one really looking at the big picture, looking at dozens of
packages, how this affects them all from the installer password
policy, to Gnome and KDE. You'd need the add user GUI tools to be able
to change both user login and encryption passphrase passwords, to keep
them in sync, and remove the old one. And currently LUKS has this 8
slot limit, which is probably not a big problem, but might be a
sufficient barrier in enough cases that this needs extending.

And so on...



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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Chris Murphy
Dennis Jacobfeuerborn denni...@conversis.de

 I'm not sure why you seem to disagree with what I wrote (unconvinced)
 and then basically say what I was saying.

you: result has to be a jack of all trades.

me: Chrome is not jack of all trades (yet) yet is very successful/growing

But also I'm unconvinced in general. I don't know how this all plays
out. But you and I are definitely on the same page with respect to
Linux with a thousand knobs popularity contest.

Granted, Windows made this work along with an army of sysadmins, so
there will be the cases where schools and governments (e.g. München,
Brasilia, etc.) and some businesses can make that work. Hopefully
there's enough understanding this is freedom/libre software and not
no cost software. That former proprietary software license budget
needs to somehow get divvied up to e.g. the Document Foundation, Linux
Foundation, FSF, whatever. The concept that's important is not no one
owns the software it's everyone owns the software. I think it's
really questionable having public dollars spend money on license fees
especially when proprietary formats get used to store public data (all
of it is public data ultimately).

But, overwhelmingly (obviously) where Linux OS's are popular are the
totally sysadmin free ones that actually have polish: Chrome OS,
Android/Cyanogen. I think it's the polish, not the fact they're mobile
OS's, that make them successful.

Kinda jaw dropping is that Microsoft is starting to get it more than
Apple when it comes to being a better citizen on multiple platform,
and they've even been contributing to the linux kernel for a while,
and open sourcing some of their own stuff, and cooperating with the
Samba folks to make everything work better. Not perfect of course, but
Apple, as much as they some things right, they really face plant in
other areas. Most of their open source effort is languishing.

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread James B. Byrne

On Thu, February 19, 2015 02:25, Niki Kovacs wrote:
 Le 19/02/2015 05:43, Chris Murphy a écrit :
 My personal view on installers is extremely biased toward the user
 staying out of trouble, they shouldn't have to read documentation
 for
 a GUI installer.

 A *user* never has to even see - or use - an installer. A USER has to
 USE a computer,  by which I mean the applications he or she needs to
 get some work done.

Outside of the corporate world, and very often at the low-end of that
itself, the user is the ADMIN.  One can purchase computer systems with
the OS and applications pre-installed of course.  But, at some point,
in every sufficiently complex and long-lived environment somebody has
to do maintenance. Which on occasion does include installing operating
systems.

And even ADMINs can use some help from time-to-time.  Let us be frank,
the Linux/GNU hoge-poge of syntax makes the English language look
positively simple in comparison. And that is not a good thing.

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Dennis Jacobfeuerborn
On 19.02.2015 19:41, Chris Murphy wrote:
 On Thu, Feb 19, 2015 at 5:47 AM, Dennis Jacobfeuerborn
 denni...@conversis.de wrote:
 I think the problem is that you simply have to draw a distinction
 between technology and product.
 The rise of the Linux desktop will never happen because Linux is not a
 product but a technology and as a result has to be a jack of all trades.
 
 I'm unconvinced. True, Chromebooks uses the linux kernel, and thus it
 qualifies, sorta, as Linux desktop. But this is something analogous to
 OS X using a FOSS kernel and some other BSD stuff, but the bulk of it
 is proprietary. Maybe Chrome isn't quite that proprietary, but it's
 not free either. And Chrome OS definitely is not jack of all trades.
 What it can run is very narrow in scope right now.
 
 
 
 The reason Apple is so successful I believe is because they understood
 more than others that people don't care about technology but want one
 specific consistent experience. They don't core how the harddisk is
 partitioned.
 So I can see the rise of the X desktop but only if X is willing to
 have its own identity an eschew the desire to be compatible with
 everything else or cater to both casual users and hard-core admin types.
 In other words the X Desktop would have to be a very opinionated
 product rather than a highly flexible technology.
 
 Hmm, well Apple as a pretty good understanding what details are and
 aren't important to most people. That is, they discriminate. People do
 care about technologies like disk encryption, but they don't care
 about the details of how to enable or manage it. Hence we see both iOS
 and Android enable it by default now. Change the screen lock password,
 and it also changes the encryption unlock password *while removing*
 the previous password all in one step. On all conventional Linux
 distributions, this is beyond confusing and is totally sysadmin
 territory. I'd call it a bad experience.
 
 OK so that's mobile vs desktop, maybe not fair. However, OS X has one
 button click full disk encryption as opt in post-install (and opt out
 after). This is done with live conversion. The user can use the
 computer normally while conversion occurs, they can put the system to
 sleep, and even reboot it, and will resume conversion when the system
 comes back up. Decrypt conversion works the same way. They are poised
 to make full disk encryption a default behavior, without having
 changed the user experience at all, in the next major release of the
 software. I don't know whether they'll do it, but there are no
 technical or usability impediments.
 
 Linux distros experience on this front is terrible. Why? Linux OS's
 don't have a good live conversion implementation (some people have
 tried this and have hacks, but no distro has adopted this); but Ok the
 installer could just enable it by default, obviating conversion. But
 there's no one really looking at the big picture, looking at dozens of
 packages, how this affects them all from the installer password
 policy, to Gnome and KDE. You'd need the add user GUI tools to be able
 to change both user login and encryption passphrase passwords, to keep
 them in sync, and remove the old one. And currently LUKS has this 8
 slot limit, which is probably not a big problem, but might be a
 sufficient barrier in enough cases that this needs extending.

I'm not sure why you seem to disagree with what I wrote (unconvinced)
and then basically say what I was saying.

Linux with a thousand knobs is never going become popular. Instead
somebody has to go and create an opinionated system where most knobs are
removed and replaced by sane/good/useful defaults. Like Google with its
Chromebooks.

Regards,
  Denis

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-19 Thread Chris Murphy
On Thu, Feb 19, 2015 at 1:38 PM, Kahlil Hodgson
kahlil.hodg...@dealmax.com.au wrote:
 On 20 February 2015 at 05:25, Chris Murphy li...@colorremedies.com wrote:
 I'd say your mom is an admin in the sense that chickens fly and horses swim.

 It's a confusing analogy. Chickens don't fly. Horses do swim.

 I have a couple of chickens, and yes, the buggers do fly if you don't
 clip their flight feathers. :-)

Ahh OK of course, short flights. Well nevertheless I do not at all
consider my mom anything remotely approaching an admin just because
she's done an OS installation...

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Michael Volz
Hi Niki,

md127 apparently only uses 81.95GB per disk. Maybe one of the partitions has 
the wrong size. What's the output of lsblk?

Regards
Michael

- Ursprüngliche Mail -
Von: Niki Kovacs i...@microlinux.fr
An: CentOS mailing list CentOS@centos.org
Gesendet: Mittwoch, 18. Februar 2015 08:09:13
Betreff: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

Hi,

I just replaced Slackware64 14.1 running on my office's HP Proliant 
Microserver with a fresh installation of CentOS 7.

The server has 4 x 250 GB disks.

Every disk is configured like this :

* 200 MB /dev/sdX1 for /boot
* 4 GB /dev/sdX2 for swap
* 248 GB /dev/sdX3 for /

There are supposed to be no spare devices.

/boot and swap are all supposed to be assembled in RAID level 1 across 4 
disks.

The / partition is supposed to be assembled in RAID level 5 across 4 disks.

With Slackware I created the arrays manually like this:

   # mdadm --create /dev/md1 --level=1 --raid-devices=4 --metadata=0.90
 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1
   # mdadm --create /dev/md2 --level=1 --raid-devices=4 --metadata=0.90
 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sdd2
   # mdadm --create /dev/md3 --level=5 --raid-devices=4 --metadata=0.90
 /dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3

Using this setup, I had 650 MB of disk space on /dev/md3.

Now I tried to do the same thing with CentOS 7. Everything seemed to 
work at first, but here's what I got now:

[root@nestor:~] # df -h
Sys. de fichiers Taille Utilisé Dispo Uti% Monté sur
/dev/md127 226G1,1G  213G   1% /
devtmpfs   1,4G   0  1,4G   0% /dev
tmpfs  1,4G   0  1,4G   0% /dev/shm
tmpfs  1,4G8,5M  1,4G   1% /run
tmpfs  1,4G   0  1,4G   0% /sys/fs/cgroup
/dev/md125 194M 80M  101M  45% /boot
/dev/sde1  917G 88M  871G   1% /mnt

The root partition (/dev/md127) only shows 226 G of space. So where has 
everything gone?

[root@nestor:~] # cat /proc/mdstat
Personalities : [raid1] [raid6] [raid5] [raid4]
md125 : active raid1 sdc2[2] sdd2[3] sdb2[1] sda2[0]
   204736 blocks super 1.0 [4/4] []

md126 : active raid1 sdd1[3] sdc1[2] sdb1[1] sda1[0]
   4095936 blocks super 1.2 [4/4] []

md127 : active raid5 sdc3[2] sdb3[1] sdd3[4] sda3[0]
   240087552 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] 
[]
   bitmap: 0/1 pages [0KB], 65536KB chunk

unused devices: none

[root@nestor:~] # mdadm -D /dev/md127
/dev/md127:
 Version : 1.2
   Creation Time : Wed Feb 18 06:49:01 2015
  Raid Level : raid5
  Array Size : 240087552 (228.97 GiB 245.85 GB)
   Used Dev Size : 80029184 (76.32 GiB 81.95 GB)
Raid Devices : 4
   Total Devices : 4
 Persistence : Superblock is persistent

   Intent Bitmap : Internal

 Update Time : Wed Feb 18 08:04:26 2015
   State : active
  Active Devices : 4
Working Devices : 4
  Failed Devices : 0
   Spare Devices : 0

  Layout : left-symmetric
  Chunk Size : 512K

Name : localhost:root
UUID : cfc13fe9:8fa811d8:85649402:58c4846e
  Events : 4703

 Number   Major   Minor   RaidDevice State
0   830  active sync   /dev/sda3
1   8   191  active sync   /dev/sdb3
2   8   352  active sync   /dev/sdc3
4   8   513  active sync   /dev/sdd3

Apparently no spare devices have been created. So why do I only have 226 
GB of disk space under CentOS, when I had roughly 650 GB under Slackware?

I'm a bit lost here. Any suggestions?

Cheers,

Niki

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread g


i am going to sit the rest of this out and read Michael's book. ;-)


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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Niki Kovacs

Le 18/02/2015 09:59, Niki Kovacs a écrit :

└─sdd3  8:51   0  76,4G  0 part
   └─md127   9:127  0   229G  0 raid5 /

Any idea what's going on ?


Ooops, just saw it. /dev/sdd3 apparently has the wrong size.

As to why this is so, it's a mystery.

I'll investigate further into this. (Since this is the office's gateway, 
I'll take some time to respond eventually. No server = no Internet :oD)


Niki

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread g


On 02/18/2015 03:01 AM, Niki Kovacs wrote:
 Le 18/02/2015 09:59, Niki Kovacs a écrit :
 └─sdd3  8:51   0  76,4G  0 part
└─md127   9:127  0   229G  0 raid5 /

 Any idea what's going on ?

 Ooops, just saw it. /dev/sdd3 apparently has the wrong size.

 As to why this is so, it's a mystery.

 I'll investigate further into this. (Since this is the office's gateway, 
 I'll take some time to respond eventually. No server = no Internet :oD)

actually, it looks like problem is with /dev/md3, not just /dev/sdd3, as
_all_ drives are wrong in their 3rd partition.


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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Michael Volz
Hi Niki,

in fact all of the sdX3 partitions are of size 76.4G. Maybe they were created 
by the installer as part of a partition scheme and you forget to resize them 
when removing other partitions from the scheme? Anyway, it should be fine if 
you recreate the partitions with the right size and then recreate the array.

Michael


- Ursprüngliche Mail -
Von: Niki Kovacs i...@microlinux.fr
An: centos@centos.org
Gesendet: Mittwoch, 18. Februar 2015 10:01:49
Betreff: Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no 
spares?

Le 18/02/2015 09:59, Niki Kovacs a écrit :
 └─sdd3  8:51   0  76,4G  0 part
└─md127   9:127  0   229G  0 raid5 /

 Any idea what's going on ?

Ooops, just saw it. /dev/sdd3 apparently has the wrong size.

As to why this is so, it's a mystery.

I'll investigate further into this. (Since this is the office's gateway, 
I'll take some time to respond eventually. No server = no Internet :oD)

Niki

-- 
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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Niki Kovacs

Le 18/02/2015 09:24, Michael Volz a écrit :

Hi Niki,

md127 apparently only uses 81.95GB per disk. Maybe one of the partitions has 
the wrong size. What's the output of lsblk?


[root@nestor:~] # lsblk
NAME  MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda 8:00 232,9G  0 disk
├─sda1  8:10   3,9G  0 part
│ └─md126   9:126  0   3,9G  0 raid1 [SWAP]
├─sda2  8:20   200M  0 part
│ └─md125   9:125  0   200M  0 raid1 /boot
└─sda3  8:30  76,4G  0 part
  └─md127   9:127  0   229G  0 raid5 /
sdb 8:16   0 232,9G  0 disk
├─sdb1  8:17   0   3,9G  0 part
│ └─md126   9:126  0   3,9G  0 raid1 [SWAP]
├─sdb2  8:18   0   200M  0 part
│ └─md125   9:125  0   200M  0 raid1 /boot
└─sdb3  8:19   0  76,4G  0 part
  └─md127   9:127  0   229G  0 raid5 /
sdc 8:32   0 232,9G  0 disk
├─sdc1  8:33   0   3,9G  0 part
│ └─md126   9:126  0   3,9G  0 raid1 [SWAP]
├─sdc2  8:34   0   200M  0 part
│ └─md125   9:125  0   200M  0 raid1 /boot
└─sdc3  8:35   0  76,4G  0 part
  └─md127   9:127  0   229G  0 raid5 /
sdd 8:48   0 232,9G  0 disk
├─sdd1  8:49   0   3,9G  0 part
│ └─md126   9:126  0   3,9G  0 raid1 [SWAP]
├─sdd2  8:50   0   200M  0 part
│ └─md125   9:125  0   200M  0 raid1 /boot
└─sdd3  8:51   0  76,4G  0 part
  └─md127   9:127  0   229G  0 raid5 /

Any idea what's going on ?

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread g


On 02/18/2015 01:23 AM, Niki Kovacs wrote:
 Le 18/02/2015 08:09, Niki Kovacs a écrit :

 Apparently no spare devices have been created. So why do I only
 have 226 GB of disk space under CentOS, when I had roughly 650 GB
 under Slackware?

 An idea just crossed my mind. Could it be that 'df' is reporting a
 wrong partition size on the RAID 5 array? And how can I check if
 this is the case?

i have not built any raid system in linux, but from reading, i saw
that there is a little difference from unix.

also, between linux flavors, there can be a lot of difference.

in a way, case of...

  who wrote the book and how whoever is reading it.

ie, Slackware and CentOS.

looking at question of 'reporting', 'df' has various ways of reporting
size and might/may/could be what is causing difference.

so, until an exact reason/cause is replied...

besides '-h', what other arguments for 'df' did you try?

  df --block-size=1000
  df --block-size=1024
  df --block-size=K
  df --block-size=M
  df --block-size=G
  df --si
  df -T

instead of reading

  man df

have a look at

  info coreutils 'df invocation'


you can also use 'lsblk', which i find it to be off a bit due to
how it rounds of sizes, except when using '-b'

'disk utility', 'system monitor', 'kde info center', 'gparted', are
other ways of viewing allocation.


much luck finding solution.


-- 

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in a world with out fences, who needs gates.

CentOS GNU/Linux 6.6

tc,hago.

g
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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Niki Kovacs

Le 18/02/2015 09:24, Michael Volz a écrit :

md127 apparently only uses 81.95GB per disk. Maybe one of the partitions has 
the wrong size. What's the output of lsblk?


I just spent a few hours experimenting with the CentOS 7 installer in a 
VirtualBox guest with four virtual hard disks. I can now confirm this is 
a very stupid bug in the (very stupid) installer. Or at least one more 
random weirdness. Here goes.


The new installer is organized around mount points, which have to be 
defined first. OK, so I first define my mountpoint /boot, set it to 200 
MB (which is enough), define it to be RAID level 1 across four disks 
with an ext2 filesystem. So far so good.


Next step is similar, swap mountpoint is 2 GB, also RAID level 1 across 
four disks.


Finally, the / (root partition) mountpoint is supposed to take up the 
full amount of remaining disk space. In my virtual guest, I defined 4 X 
40 GB to fiddle with. The installer shows me something like 38.6 GB, 
which looks like the remaining space on each disk's partition.


Now I define RAID level 5 across four disks...

... and here it comes.

Once RAID level 5 is defined, I have to REDEFINE the maximum disk space 
by putting in a random large number, for example 4 X 40 GB = 160 GB. 
Because what is meant here is THE TOTAL RESULTING AMOUNT OF DISK SPACE 
IN THE RAID 5 ARRAY, AND NOT THE MAXIMUM SIZE OF A DISK PARTITION. So 
once I fill that field with 160 GB, the installer automagically sets 
it to 106.8 GB, which is in effect the maximum available disk space 
using RAID 5.


Usability anyone?

Cheers from the sunny South of France,

Niki Kovacs
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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Chris Murphy
On Wed, Feb 18, 2015 at 1:21 PM, Niki Kovacs i...@microlinux.fr wrote:
 Le 18/02/2015 09:24, Michael Volz a écrit :

 md127 apparently only uses 81.95GB per disk. Maybe one of the partitions
 has the wrong size. What's the output of lsblk?


 I just spent a few hours experimenting with the CentOS 7 installer in a
 VirtualBox guest with four virtual hard disks. I can now confirm this is a
 very stupid bug in the (very stupid) installer. Or at least one more random
 weirdness. Here goes.

 The new installer is organized around mount points, which have to be defined
 first. OK, so I first define my mountpoint /boot, set it to 200 MB (which is
 enough), define it to be RAID level 1 across four disks with an ext2
 filesystem. So far so good.

 Next step is similar, swap mountpoint is 2 GB, also RAID level 1 across four
 disks.

 Finally, the / (root partition) mountpoint is supposed to take up the full
 amount of remaining disk space. In my virtual guest, I defined 4 X 40 GB to
 fiddle with. The installer shows me something like 38.6 GB, which looks like
 the remaining space on each disk's partition.

 Now I define RAID level 5 across four disks...

 ... and here it comes.

 Once RAID level 5 is defined, I have to REDEFINE the maximum disk space by
 putting in a random large number, for example 4 X 40 GB = 160 GB. Because
 what is meant here is THE TOTAL RESULTING AMOUNT OF DISK SPACE IN THE RAID 5
 ARRAY, AND NOT THE MAXIMUM SIZE OF A DISK PARTITION. So once I fill that
 field with 160 GB, the installer automagically sets it to 106.8 GB, which
 is in effect the maximum available disk space using RAID 5.

 Usability anyone?

installer is organized around mount points is correct, and what gets
mounted on mount points? Volumes, not partitions. So it's consistent
with the UI that the size is a volume size, not a partition size.

The problem here, is that users are used to being involved in details
like making specific partitions in a specific order with specific
sizes. The new UI de-emphasizes the need to be involved in that level
of detail. It ends up making things more consistent regardless of
which device type you use: LVM, LVM thinp, standard, or Btrfs. If
you emphasize partitions, then you have to emphasize the user needing
to know esoteric things.

What is NOT obvious: for single device installs, if you omit the size
in the create mount point dialog, the size of the resulting volume
will consume all remaining space. But since there's no way to preset
raid5 at the time a mount point is created (raid5 is set after the
fact), there isn't a clear way to say use all remaining space for
this. There's just a size field for the volume, and a space available
value in the lower left hand corner.

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Niki Kovacs

Le 18/02/2015 23:12, Chris Murphy a écrit :

installer is organized around mount points is correct, and what gets
mounted on mount points? Volumes, not partitions.


Says who?

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Niki Kovacs

Le 19/02/2015 05:43, Chris Murphy a écrit :

My personal view on installers is extremely biased toward the user
staying out of trouble, they shouldn't have to read documentation for
a GUI installer.


A *user* never has to even see - or use - an installer. A USER has to 
USE a computer,  by which I mean the applications he or she needs to get 
some work done.


The person who gets to be confronted by an OS installer is not a user, 
it's an ADMIN, which is an entirely different thing. An ADMIN should 
RTFM (a lot) and know his way about what you call esoteric things 
earlier in this thread (disks, partitions, volumes).


My company (http://www.microlinux.fr) installs complete Linux-based 
networks for schools, town halls, public libraries etc. here in South 
France. For now, most of my server and desktop solutions are based on a 
highly modified version of Slackware Linux, with some CentOS and some 
RHEL here and there. I'm currently planning on migrating everything to 
CentOS in the long run.


One of the founding principles of my company is the constant SEPARATION 
BETWEEN USING A COMPUTER AND ADMINISTRATING IT. A user never ever has to 
worry about things that pertain to system administration, and it would 
be very wrong if he or she ever has to deal with such a thing as an 
installer. For what it's worth, some of my users don't even know that 
this thing that they're using every day is called Linux under the hood. 
To them, it's just the machine that's running things like their library 
management software, or whatever.


So, as an admin, what I want from an installer is FLEXIBILITY... and not 
an assistant that reminds me of Microsoft Office's infamous Clippy and 
expects me to jump through burning loops to configure the system as I 
want it.


Cheers,

Niki

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread John R Pierce

On 2/18/2015 11:06 PM, John R Pierce wrote:


 but, is that lvm integrated raid stuff available in RHEL/CentOS 6 
or 7 yet ? 


/me scribbles postit note to self:   google BEFORE hitting send

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/raid_volumes.html

ahhh, interesting.  its in 6.3+



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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Chris Murphy
On Wed, Feb 18, 2015 at 3:59 PM, Niki Kovacs i...@microlinux.fr wrote:
 Well, maybe it's just me. I've started Linux on Slackware 7.1 and used
 pretty much every major and minor distribution under the sun. I know my way
 around Slackware, Debian, CentOS, FreeBSD, Gentoo, Arch and many more, and
 my favourite installer is - and will always be - Slackware's bone-headed
 NCurses installer that lets the admin do pretty much what he wants - and
 needs - to do.

I'm definitely not suggesting it's just you. I'm coming up with a
plausible explanation for the confusion, and that's a misalignment
between your expectations and the installer's presentation. I can tell
you, having using this installer since Fedora 18, it has changed
immensely from the initial versions.

My personal view on installers is extremely biased toward the user
staying out of trouble, they shouldn't have to read documentation for
a GUI installer. The entire point of a GUI installer is to protect the
user from bad choices, non-standard or unsupportable choices, or
having to read a volume of documentation, or become an expert for
something that quite frankly happens rarely: OS installation.

And my very strong bias is affected by both the OS X and Windows
installers, which are completely, utterly, brain dead. And I mean that
in a good way. It's impossible for the user to get confused, there are
almost no choices. It's next to impossible for there to be bugs, there
are almost no choices. Every outcome of the installation is
supportable, because the user wasn't allowed to create completely
nutty layouts that make no sense.

Now, for various reasons Anaconda (the Fedora/RHEL/CentOS installer)
is exceptionally more capable than almost any other GUI installer out
there. And that makes it complex, prone to bugs, and prone to
confusing users and subject to criticism. That's just the inevitable
result of trying to do so many things.



 I love CentOS, been using it since 4.x. But frankly, CentOS 7's installer is
 an abomination.

Having done many hundreds, possibly over a thousand installations with
it, I'm well aware of how confusing it can be. So the criticism is
almost certainly reasonable, no matter what. I'm just saying that once
you understand the point of view of the installer (which arguably you
should not have to do), things become much easier. That doesn't mean
easy. Just easier.


 All's well that ends well. It only took me a day and a half to figure out
 how to configure RAID 5 using the graphical assistant. Something I could
 have done in less than three minutes using fdisk and mdadm --create.

Right, but inevitably that failure is the result of misalignment of
expectations between you and the installer. That's an explanation, not
an assignment of blame. The reason why working directly with
partitions is easy for you, and what you expect, is simply because
that's how you've always done it, since  that's how all other
installers behave. Anaconda is really the first installer that
deemphasizes that. And I think that's a bold move, and for a GUI
installer that's necessarily taking on a lot of complexity I think
it's probably a good idea overall. But it does have a lot of bugs
still... it's definitely doing things that I don't like.

But any experienced sysadmin knows how users say it should work like
X and how often they're wrong. They're just used to things that work
like X and that's why they want this new problem to work that same
way. So as a sysadmin or network engineer you ask questions to find
out how to get the user from A to B, and the details of how it should
work are your domain, your specialty, and ultimately they don't
really care how it happens, they just want to get to B. And once
that's well understood, you can get on with things.

And one problem is the installer can't really have that kind of
diplomatic conversation about what its worldview is, so that the user
expectations re-align with the end goal in mind, not how to get there.

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Chris Murphy
On Wed, Feb 18, 2015 at 3:37 PM, Niki Kovacs i...@microlinux.fr wrote:
 Le 18/02/2015 23:12, Chris Murphy a écrit :

 installer is organized around mount points is correct, and what gets
 mounted on mount points? Volumes, not partitions.


 Says who?

Because it's ambiguous. A partition might entirely contain a volume (a
filesystem), but in your case none of your partitions contain a
volume. They're members of md raid first, only once that's assembled
is there a logical block device, which happens to contain the volume,
and it is the volume you're mounting. All you have to do is check
fstab, partitions aren't assigned mount points, volumes are.


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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Chris Murphy
On Wed, Feb 18, 2015 at 4:20 PM,  m.r...@5-cent.us wrote:
 Niki Kovacs wrote:
 Le 18/02/2015 23:12,

 close, but then, for mysterious reasons, Red Hat decided to cripple it
 into oblivion. Go figure.

 One word: desktop. That's what they want to conquer next.

OK well there's a really long road to get to that pie in the sky. I
don't see it happening because it seems there's no mandate to
basically tell people what they can't have, instead it's well, we'll
have a little of everything.

Desktop OS that are the conquerers now? Their installers don't offer
100's of layout choices. They offer 1-2, and they always work rock
solid, no crashing, no user confusion, essentially zero bugs. The code
is brain dead simple, and that results in stability.

*shrug*

Long road. Long long long. Tunnel. No light. The usability aspects are
simply not taken seriously by the OS's as a whole. It's only taken
seriously by DE's and they get loads of crap for every change they
want to make. Until there's a willingness to look at 16 packages as a
whole rather than 1 package at a time, desktop linux has no chance.
The very basic aspects of how to partition, assemble, and boot and
linux distro aren't even agreed upon. Fedora n+1 has problems
installing after Fedora n. And it's practically a sport for each
distro to step on an existing distros installer. This is
technologically solved, just no one seems to care to actually
implement something more polite.

OS X? It partitions itself, formats a volume, sets the type code,
writes some code into NVRAM, in order to make the reboot automatically
boot the Windows installer from a USB stick. It goes out of it's way
to invite the foreign OS.

We can't even do that with the same distro, different version. It
should be embarrassing but no one really cares enough to change it.
It's thankless work in the realm of polish. But a huge amount of
success for a desktop OS comes from polish.


 We also pretty much don't use any drives under 1TB. The upshot is we had
 custom scripts for  500GB, which made 4 partitions - /boot (1G, to fit
 with the preupgrade), swap (2G), / (497G - and we're considering
 downsizing that to 250G, or maybe 150G) and the rest in another partition
 for users' data and programs. The installer absolutely does *not* want to
 do what we want. We want swap - 2G - as the *second* partition. But if we
 use the installer, as soon as we create the third partition, of 497GB, for
 /, it immediately reorders them, so that / is second.

I'm open to having my mind changed on this, but I'm not actually
understanding why it needs to be in the 2nd slot, other than you want
it there, which actually isn't a good enough reason. If there's a good
reason for it to be in X slot always, for everyone, including
anticipating future use, then that's a feature request and it ought to
get fixed. But if it's a specific use case, well yeah you get to
pre-partition and then install.

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread John R Pierce

On 2/18/2015 8:20 PM, Chris Murphy wrote:

On Wed, Feb 18, 2015 at 3:37 PM, Niki Kovacsi...@microlinux.fr  wrote:

Le 18/02/2015 23:12, Chris Murphy a écrit :


installer is organized around mount points is correct, and what gets
mounted on mount points? Volumes, not partitions.



Says who?

Because it's ambiguous. A partition might entirely contain a volume (a
filesystem), but in your case none of your partitions contain a
volume. They're members of md raid first, only once that's assembled
is there a logical block device, which happens to contain the volume,
and it is the volume you're mounting. All you have to do is check
fstab, partitions aren't assigned mount points, volumes are.


and I make my mdraid's PV's for lvm, and create LV's that are my file 
systems which I mount.  so thats one MORE level of indirection.


disks - partition(s) - mdraid devices - PVs - VG - LV - file 
system.   phew.






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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Chris Murphy
On Wed, Feb 18, 2015 at 9:25 PM, John R Pierce pie...@hogranch.com wrote:

 disks - partition(s) - mdraid devices - PVs - VG - LV - file system.
 phew.

You might be a candidate for LVM integrated raid. It uses the md
kernel code on the backend, but it's all LVM tools to create, manage
and monitor. The raid level is defined per LV, instead of all LV's in
a VG inheriting the underlying raid. It supports all levels of raid
including 5/6.

It doesn't quite have all the features of mdadm. But the flexibility
it offers for use cases where LV's are often being created and
destroyed and different redundancy levels/types are desired, it's
neat.

And eventually, one of these years, Btrfs. That is so much simpler to
create and manage.

diskno partitionBtrfsraidsubvolumes instead of partitions

It doesn't have all the features of mdadm or lvm, especially when it
comes to VM images. But for general purpose data, it's nice. It'll use
different sized drives in a raid56, no fuss, no having to tell it how
to do that. Online addition of yet another (unlike sized) drive and it
just starts using it with a single 'btrfs device add' command. No
restripe/resilver needed.

-- 
Chris Murphy
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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread John R Pierce

On 2/18/2015 9:39 PM, Chris Murphy wrote:

You might be a candidate for LVM integrated raid. It uses the md
kernel code on the backend, but it's all LVM tools to create, manage
and monitor. The raid level is defined per LV, instead of all LV's in
a VG inheriting the underlying raid. It supports all levels of raid
including 5/6. ... ...
...
... ... btrfs ...


actually, I prefer zfs.   I was just saying how I do it on CentOS, where 
zfs is not really an option.


# zpool create zbig mirror hd10 hd11 mirror hd12 hd13 mirror hd14 hd15 
mirror hd16 hd17 mirror hd18 hd19 spare hd20 hd21

# zfs create -o mountpoint=/mystuff zbig/mystuff

done.

 but, is that lvm integrated raid stuff available in RHEL/CentOS 6 
or 7 yet ?



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john r pierce  37N 122W
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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread Niki Kovacs

Le 18/02/2015 23:12, Chris Murphy a écrit :

What is NOT obvious: for single device installs, if you omit the size
in the create mount point dialog, the size of the resulting volume
will consume all remaining space. But since there's no way to preset
raid5 at the time a mount point is created (raid5 is set after the
fact), there isn't a clear way to say use all remaining space for
this. There's just a size field for the volume, and a space available
value in the lower left hand corner.


Well, maybe it's just me. I've started Linux on Slackware 7.1 and used 
pretty much every major and minor distribution under the sun. I know my 
way around Slackware, Debian, CentOS, FreeBSD, Gentoo, Arch and many 
more, and my favourite installer is - and will always be - Slackware's 
bone-headed NCurses installer that lets the admin do pretty much what he 
wants - and needs - to do. CentOS 5.x's text mode installer got pretty 
close, but then, for mysterious reasons, Red Hat decided to cripple it 
into oblivion. Go figure.


I love CentOS, been using it since 4.x. But frankly, CentOS 7's 
installer is an abomination.


All's well that ends well. It only took me a day and a half to figure 
out how to configure RAID 5 using the graphical assistant. Something I 
could have done in less than three minutes using fdisk and mdadm --create.


Cheers,

Niki

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-18 Thread m . roth
Niki Kovacs wrote:
 Le 18/02/2015 23:12, Chris Murphy a écrit :
 What is NOT obvious: for single device installs, if you omit the size
 in the create mount point dialog, the size of the resulting volume
 will consume all remaining space. But since there's no way to preset
 raid5 at the time a mount point is created (raid5 is set after the
 fact), there isn't a clear way to say use all remaining space for
 this. There's just a size field for the volume, and a space available
 value in the lower left hand corner.
snip
 close, but then, for mysterious reasons, Red Hat decided to cripple it
 into oblivion. Go figure.

One word: desktop. That's what they want to conquer next.

 I love CentOS, been using it since 4.x. But frankly, CentOS 7's
 installer is an abomination.

 All's well that ends well. It only took me a day and a half to figure
 out how to configure RAID 5 using the graphical assistant. Something I
 could have done in less than three minutes using fdisk and mdadm --create.

We don't want to use lvm - my manager doesn't like it, and given how much
we hit our machines, we almost don't use vm's, either - we need all CPU
cycles for some things (like heavy scientific computing).

We also pretty much don't use any drives under 1TB. The upshot is we had
custom scripts for  500GB, which made 4 partitions - /boot (1G, to fit
with the preupgrade), swap (2G), / (497G - and we're considering
downsizing that to 250G, or maybe 150G) and the rest in another partition
for users' data and programs. The installer absolutely does *not* want to
do what we want. We want swap - 2G - as the *second* partition. But if we
use the installer, as soon as we create the third partition, of 497GB, for
/, it immediately reorders them, so that / is second.

Duh

The result is that we get to the screen to choose the drive, and say
custom partition... then alt-F2, and use parted to make the
partitions, then go back to the GUI and just assign the mount points and
filesystem types.

And why would you *want* / to have everything? I want to be able to
install a newer o/s, or whatever, and not have to worry about all the
data, etc - I want that in a separate partition (no, don't format that,
thank you).

   mark

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Re: [CentOS] CentOS 7: software RAID 5 array with 4 disks and no spares?

2015-02-17 Thread Niki Kovacs

Le 18/02/2015 08:09, Niki Kovacs a écrit :



Apparently no spare devices have been created. So why do I only have 226
GB of disk space under CentOS, when I had roughly 650 GB under Slackware?



An idea just crossed my mind. Could it be that 'df' is reporting a wrong 
partition size on the RAID 5 array? And how can I check if this is the case?



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