Re: [CentOS] Centos 7 RAID tutorial?
On 11.09.2014 01:27, Scott Robbins wrote: In contrast, the CentOS wiki article, if running CentOS 5 or 6, gives an easy to follow guide, complete with commands one might actually type. (At least some of the instructions don't seem to work with CentOS 7 though) Did you read the topic of this thread? This is about version 7 ;) furthermore, which wiki article are you referring to? the search yields many results like: http://wiki.centos.org/HowTos/CentOS5ConvertToRAID?highlight=%28raid%29 which might be not what you want, depending on what you want. I'm no fan of copy and paste tutorials if they are not used just for very specific use cases. and just using a centos 5 tutorial on centos 7 seems not to be the best way to start things. ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On Thu, Sep 11, 2014 at 09:48:36PM +0200, Sven Kieske wrote: On 11.09.2014 01:27, Scott Robbins wrote: In contrast, the CentOS wiki article, if running CentOS 5 or 6, gives an easy to follow guide, complete with commands one might actually type. (At least some of the instructions don't seem to work with CentOS 7 though) Did you read the topic of this thread? This is about version 7 ;) Sorry, I wasn't clear, and I apologize. My point is that the tutorial, which at least judging from my experience, won't work in 7, is detailed and helpful for both novice and the more experienced. In contrast, the upstream seems as if they basically paid someone to dress up read the man page, in 10 pages. furthermore, which wiki article are you referring to? the search yields many results like: http://wiki.centos.org/HowTos/CentOS5ConvertToRAID?highlight=%28raid%29 Again, apologies. Some mental shorthand on my part, as I was recently using that article in a work situation. I meant this one. http://wiki.centos.org/HowTos/Install_On_Partitionable_RAID1 Which I suppose you can call it cut and paste. Now, I did, for my own knowledge, see if I could get that to work on CentOS-7, but I couldn't. which might be not what you want, depending on what you want. I'm no fan of copy and paste tutorials if they are not used just for very specific use cases. and just using a centos 5 tutorial on centos 7 seems not to be the best way to start things. I don't know how much knowledge the OP has or doesn't have. I don't think it's unreasonable to expect instructions to include examples and commands, but we're now very much outside the scope of this thread. :) TL;DR I wasn't clear. My point, in one sentence is that I don't consider the RH documentation very good, and a tutorial for CentOS 7, written in the style of the tutorial to which I link, would be far more helpful. -- Scott Robbins PGP keyID EB3467D6 ( 1B48 077D 66F6 9DB0 FDC2 A409 FA54 EB34 67D6 ) gpg --keyserver pgp.mit.edu --recv-keys EB3467D6 ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
Quoting Digimer li...@alteeve.ca: On 10/09/14 06:45 PM, Dave Stevens wrote: Quoting Digimer li...@alteeve.ca: On 10/09/14 05:35 PM, Eliezer Croitoru wrote: On 09/10/2014 02:33 AM, Digimer wrote: The problem with ZFS on linux is license related more than technical. It exists for ubutnu so I can use it from a ppa for testing. I would like to understand more about this license issue. If you can sound me with more about it will help me understand the issue. Thanks, Eliezer http://zfsonlinux.org/faq.html#WhatAboutTheLicensingIssue https://en.wikipedia.org/wiki/ZFS#Linux -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos Dear All, This list reminds me of the wizards in the Terry Pratchett novels - confronted with a need to take action they would by far rather discuss all possibilities, however remote, than address the need in a simple way, after all they're WIZARDS. The discussion has been pretty interesting, I've figured out what I wanted to know through other means. Thanks for the perspectives. Dave Hi Dave, I can understand your feeling, but I need to say that storage, as a topic, is a very big one. People form entire careers around the topic. So when discussing storage without a specific context, conversations like this are inevitable. All the points that have been made in this thread are valid and important. So I suppose the better thing would be, if you were still looking for answers, would be to ask the question with a particular use-case in mind. That would allow people to stay more focused in their answers. Cheers! digimer Quoting Digimer li...@alteeve.ca: On 10/09/14 06:45 PM, Dave Stevens wrote: Quoting Digimer li...@alteeve.ca: On 10/09/14 05:35 PM, Eliezer Croitoru wrote: On 09/10/2014 02:33 AM, Digimer wrote: The problem with ZFS on linux is license related more than technical. It exists for ubutnu so I can use it from a ppa for testing. I would like to understand more about this license issue. If you can sound me with more about it will help me understand the issue. Thanks, Eliezer http://zfsonlinux.org/faq.html#WhatAboutTheLicensingIssue https://en.wikipedia.org/wiki/ZFS#Linux -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos Dear All, This list reminds me of the wizards in the Terry Pratchett novels - confronted with a need to take action they would by far rather discuss all possibilities, however remote, than address the need in a simple way, after all they're WIZARDS. The discussion has been pretty interesting, I've figured out what I wanted to know through other means. Thanks for the perspectives. Dave Hi Dave, I can understand your feeling, but I need to say that storage, as a topic, is a very big one. People form entire careers around the topic. So when discussing storage without a specific context, conversations like this are inevitable. All the points that have been made in this thread are valid and important. So I suppose the better thing would be, if you were still looking for answers, would be to ask the question with a particular use-case in mind. That would allow people to stay more focused in their answers. Cheers! digimer Ok, maybe one more. I manage a server with CentOS 5.10 that has a raid 10 array with a hot spare. It was well set up by someone else and has worked very well. It also has a Xen kernel and several VMs, also all working well. The age of the OS and accumulated cruft in the application side, together with the absence of the person who did the original setup, have me thinking about a new clean install - first on a transitional box for continuity, then a new config on the current hardware with the same basic design but more up-to-date; we are now a long way from version 5.3. I had seen reference to a much improved raid installation procedure in version 7. I can now confirm that the process is indeed much simpler and so I have been able to get on with performance testing in various scenarios, which was what I wanted to do. My experience has been that of you want a tutorial on any topic the internet is flooded with the. But I didn't see one for this topic, so I thought a routine query on this list would get me a starting point. That didn't exactly happen. But there's lots of food for thought in the answers I got and I'll be able to take at least some of that forward. And if I'm motivated enough may I'LL make the tutorial! Dave -- Digimer Papers and Projects: https://alteeve.ca/w/
Re: [CentOS] Centos 7 RAID tutorial?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Thanks for the clarification and the link! No need to apologize, I tend to forget thinks myself from time to time. kind regards Sven -BEGIN PGP SIGNATURE- Version: GnuPG v2.0.22 (MingW32) iQGcBAEBAgAGBQJUEio1AAoJEAq0kGAWDrqlKcwMAIUdQyFdlya1Q27zN0UGsI7r Hh4w0kUGVL66Ar5n1OcgAiHavFtNFsShowqen6uh12Pjv6yir74rulaGNPeI8yq5 oxMzLuEzIwRMkMO3rjPDJBjS5vRURrIA6/ldUTtz5cAscrezKx8NHuYWHmGdRK81 VyKmIjGvNIobVqVGk3qEcsyB2S/BEX1W0ZHyikP2rokPGhM/XD9+2TYkA6q/ee7q k4HiBXXOMXkCmVkq/S+KAWZHfN9i1QBx4M2MB4PoNUPya49Ei4YQWe6KFhT+YT/D xA14eG1SEonz10OhN9z7LzI3ZNxo330PHP+Xz7ggAwe4OY2SrQ7jGIZEko/CkycJ 6GMiiY3Ou4GvVB9gQ0HefRddlRl/lQTIeUVjCQcl1y01FBxPyhhq6pAo9D1O9k5R 1/0JTt+/W8GZ+yCfjbnMama20tA69yf4PRkWXAs89oW0rsZANr2fxYghMucv07fp aIqzR4uL9ORsuYY+YWIwSR1wlpDpCisRJ/yV3gckIg== =Be1t -END PGP SIGNATURE- ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On Fri, Sep 12, 2014 at 01:03:17AM +0200, Sven Kieske wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Thanks for the clarification and the link! No need to apologize, I tend to forget thinks myself from time to time. Thanks for the understanding. :) Mental shorthand is a bad habit of mine. -- Scott Robbins PGP keyID EB3467D6 ( 1B48 077D 66F6 9DB0 FDC2 A409 FA54 EB34 67D6 ) gpg --keyserver pgp.mit.edu --recv-keys EB3467D6 ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 09/10/2014 02:33 AM, Digimer wrote: The problem with ZFS on linux is license related more than technical. It exists for ubutnu so I can use it from a ppa for testing. I would like to understand more about this license issue. If you can sound me with more about it will help me understand the issue. Thanks, Eliezer ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 10/09/14 05:35 PM, Eliezer Croitoru wrote: On 09/10/2014 02:33 AM, Digimer wrote: The problem with ZFS on linux is license related more than technical. It exists for ubutnu so I can use it from a ppa for testing. I would like to understand more about this license issue. If you can sound me with more about it will help me understand the issue. Thanks, Eliezer http://zfsonlinux.org/faq.html#WhatAboutTheLicensingIssue https://en.wikipedia.org/wiki/ZFS#Linux -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
Quoting Digimer li...@alteeve.ca: On 10/09/14 05:35 PM, Eliezer Croitoru wrote: On 09/10/2014 02:33 AM, Digimer wrote: The problem with ZFS on linux is license related more than technical. It exists for ubutnu so I can use it from a ppa for testing. I would like to understand more about this license issue. If you can sound me with more about it will help me understand the issue. Thanks, Eliezer http://zfsonlinux.org/faq.html#WhatAboutTheLicensingIssue https://en.wikipedia.org/wiki/ZFS#Linux -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos Dear All, This list reminds me of the wizards in the Terry Pratchett novels - confronted with a need to take action they would by far rather discuss all possibilities, however remote, than address the need in a simple way, after all they're WIZARDS. The discussion has been pretty interesting, I've figured out what I wanted to know through other means. Thanks for the perspectives. Dave -- We hang petty thieves and appoint great ones to office -- Aesop ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 09/11/2014 01:27 AM, Digimer wrote: On 10/09/14 05:35 PM, Eliezer Croitoru wrote: On 09/10/2014 02:33 AM, Digimer wrote: The problem with ZFS on linux is license related more than technical. It exists for ubutnu so I can use it from a ppa for testing. I would like to understand more about this license issue. If you can sound me with more about it will help me understand the issue. Thanks, Eliezer http://zfsonlinux.org/faq.html#WhatAboutTheLicensingIssue https://en.wikipedia.org/wiki/ZFS#Linux Thanks! ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On 11.09.2014 00:45, Dave Stevens wrote: Dear All, This list reminds me of the wizards in the Terry Pratchett novels - confronted with a need to take action they would by far rather discuss all possibilities, however remote, than address the need in a simple way, after all they're WIZARDS. The discussion has been pretty interesting, I've figured out what I wanted to know through other means. Thanks for the perspectives. Dave I am under the same sad (and a little funny) impression. But for people who may have the same problem I guess here is a good answer, obvious somehow, but hey, nobody gave it until now: Just follow upstream documentation: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Storage_Administration_Guide/ch-raid.html HTH Sven -BEGIN PGP SIGNATURE- Version: GnuPG v2.0.22 (MingW32) iQGcBAEBAgAGBQJUENfyAAoJEAq0kGAWDrqlSZ4L/0apJQjggIa4J8tK+qh923J9 wxLC9/eyNjevWv7dnIsyrYI0PPqFtc9DYYEuLhJo2dnS1eHA9nslTxxdNUte/UEL QvEq9i20afFS5iculK7y/1U6EtTZeDh677KuyW4yZzYqQoixN8Af2ZFqMVW3VLi1 wP5fB93nhEu2w4BybVtJnOeL67MyYZprhyUOJgZquZEgvAJzmvhA71PccuOPSBvl HAnOmMoigUohS6gOwn3Zwg8Zf4snHuEEmq2owdrG18ygIi4XbmIbzSynQnAGgCSo BGDdRYyecQbE3e0rSdplY6len/fWd61KIi8XxtXK2Y4Ip8EE03ae4WhHUhX6q7UQ 3riMRmPJ+2NmY1utYqqEsUZxe1VXqieA5/MrxM5A2XFf5hazqOUZJBir5RqBnYWl O15tY5aGg4ogoCk2VgbRnKlpWMscfvosYM1qeNmLCwUbsNfvHVEv6coS0iaonB2D aohSSSG9gTDTk7UTFtNvza1ubCALcBncW7rUplRV6g== =gIjm -END PGP SIGNATURE- ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 10/09/14 06:45 PM, Dave Stevens wrote: Quoting Digimer li...@alteeve.ca: On 10/09/14 05:35 PM, Eliezer Croitoru wrote: On 09/10/2014 02:33 AM, Digimer wrote: The problem with ZFS on linux is license related more than technical. It exists for ubutnu so I can use it from a ppa for testing. I would like to understand more about this license issue. If you can sound me with more about it will help me understand the issue. Thanks, Eliezer http://zfsonlinux.org/faq.html#WhatAboutTheLicensingIssue https://en.wikipedia.org/wiki/ZFS#Linux -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos Dear All, This list reminds me of the wizards in the Terry Pratchett novels - confronted with a need to take action they would by far rather discuss all possibilities, however remote, than address the need in a simple way, after all they're WIZARDS. The discussion has been pretty interesting, I've figured out what I wanted to know through other means. Thanks for the perspectives. Dave Hi Dave, I can understand your feeling, but I need to say that storage, as a topic, is a very big one. People form entire careers around the topic. So when discussing storage without a specific context, conversations like this are inevitable. All the points that have been made in this thread are valid and important. So I suppose the better thing would be, if you were still looking for answers, would be to ask the question with a particular use-case in mind. That would allow people to stay more focused in their answers. Cheers! digimer -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On Thu, Sep 11, 2014 at 01:00:02AM +0200, Sven Kieske wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On 11.09.2014 00:45, Dave Stevens wrote: Dear All, This list reminds me of the wizards in the Terry Pratchett novels - confronted with a need to take action they would by far rather discuss all possibilities, however remote, than address the need in a simple way, after all they're WIZARDS. The discussion has been pretty interesting, I've figured out what I wanted to know through other means. Thanks for the perspectives. Dave I am under the same sad (and a little funny) impression. But for people who may have the same problem I guess here is a good answer, obvious somehow, but hey, nobody gave it until now: Just follow upstream documentation: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Storage_Administration_Guide/ch-raid.html Page one. Define RAID. Page 2, who should use it. Configuring Raid (after a few more wasted pages). Read the man page. It seems too sparse for a beginner and, with such sparseness, not much use to an experienced admin. I can't see that being very useful to someone with little or no RAID experience. (And actually, it's so sparse that the experienced won't need the little bit of suggestion it gives.) In contrast, the CentOS wiki article, if running CentOS 5 or 6, gives an easy to follow guide, complete with commands one might actually type. (At least some of the instructions don't seem to work with CentOS 7 though) -- Scott Robbins PGP keyID EB3467D6 ( 1B48 077D 66F6 9DB0 FDC2 A409 FA54 EB34 67D6 ) gpg --keyserver pgp.mit.edu --recv-keys EB3467D6 ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On Mon, Sep 8, 2014 at 2:58 PM, Dave Stevens g...@uniserve.com wrote: This is a pretty interesting discussion but has not revealed an on-line tutorial. Anyone? Dave Use mdadm commands. ~]$ man mdadm I don't follow any one tutorial or guide in particular, I consult the mdadm manpage in most cases. Though, the following URLs look to have suitable information (at a quick glance): https://raid.wiki.kernel.org/index.php/RAID_setup http://www.ducea.com/2009/03/08/mdadm-cheat-sheet/ http://www.mysolutions.it/tutorial-mdadm-software-raid-ubuntu-debian-systems/ -- ---~~.~~--- Mike // SilverTip257 // ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 09/08/2014 10:00 PM, Andrew Holway wrote: +1 Try ZFS http://zfsonlinux.org/ How stable is it on linux? Eliezer ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 09/09/14 05:36 PM, Eliezer Croitoru wrote: On 09/08/2014 10:00 PM, Andrew Holway wrote: +1 Try ZFS http://zfsonlinux.org/ How stable is it on linux? Eliezer The problem with ZFS on linux is license related more than technical. -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 09/07/2014 09:19 PM, Dave Stevens wrote: I want to set up a new CentOS install using version 7 and would like to experiment with various RAID levels. Anyone care to point out a tutorial? That's a very broad question, so the responses thus far shouldn't be surprising. I suggest reading: http://en.wikipedia.org/wiki/RAID Figure out approximately what you want to do, and come back with any questions. Sound good? -- Ian Pilcher arequip...@gmail.com I grew up before Mark Zuckerberg invented friendship ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 2014-09-09, Eliezer Croitoru elie...@ngtech.co.il wrote: How stable is it on linux? My own experience is very limited, but I have heard from a handful of reliable sources who are very happy with ZFS. As Digimer noted, much of the challenge is in the licensing, not a technical issue. ZFS has been packaged for RHEL/CentOS: http://zfsonlinux.org/epel.html So it should be fairly straightforward to get things working. (If you've installed your own kernel you may need the generic RPM packages instead.) --keith -- kkel...@wombat.san-francisco.ca.us ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 9/7/2014 8:09 PM, Digimer wrote: I'm not so familiar with software RAID, but I would be surprised if there isn't a way to force write-through caching. If this is possible, then Valeri's concern can be addressed (at the cost of performance). software raid on enterprise grade JBOD *is* write-through caching. the OS will only cache writes til an fsync/fdatasync/etc and then it will flush them to the md device, which will immediately flush them to the physical media.where it goes sideways is when you use cheap consumer grade desktop drives, those often lie about write complete to improve windows performance... but these would be a problem with or without mdraid, indeed, they would be a problem with hardware raid, too. this is why I really like ZFS (on solaris and bsd, at least), because it timestamps and checksums every block it writes to disk... a conventional raid1, if the two copies don't match, you don't know which one is the 'right' one. the ZFS scrub process will check these timestamps and crc's, and correct the 'wrong' block. I did a fair bit of informal(*) benchmarking of some storage systems at work before they were deployed. using a hardware raid card such as a LSI Megaraid 9260 with 2GB BBU cache, (or HP P410i or similar) is most certainly faster at transactional database style random read/write testing than using a simple SAS2 JBOD controller.But using mdraid with the Megaraid configured just as a bunch of disks, gave the same results if writeback caching was enabled in the controller. At different times, using different-but-similar SAS2 raid cards, I benchmarked 10-20 disk raids in various levels like 10, 5, 6, 50, and 60, built with 7200RPM SAS2 'nearline server' drives, 7200rpm SATA desktop drives, and 15000rpm SAS2 enterprise server drives.For an OLTP style database server under high concurrency and high transaction/second rates, raid10 with lots of 15k disks is definitely the way to go. for bulk file storage that's write-once and read-mostly, raid 5, 6, 60 perform adequately. (*) my methodology was ad-hoc rather than rigorous, I primarily observed trends, so I can't publish any hard data to back these conclusions.. My tests including postgresql with pgbench, and various bonnie++ and iozone tests. most of these tests were on Xeon X5600 class servers with 8-12 cores, and 24-48GB ram. -- john r pierce 37N 122W somewhere on the middle of the left coast ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
Quoting Digimer li...@alteeve.ca: On 07/09/14 11:01 PM, Keith Keller wrote: On 2014-09-08, Valeri Galtsev galt...@kicp.uchicago.edu wrote: Even more: system failure or power loss is more likely to destroy all data on software RAID than on a single drive when there is a lot of IO present (to the best of my understanding, loss of cache software RAID is using is more catastrophic compared to journaled filesystem under same circumstances - somebody may correct me). So, there may be worth thinking about hardware RAID. I think an essential feature of any md RAID that's not a RAID1 is a UPS and a mechanism for a clean shutdown in case of extended power failure. (An md RAID1 might be okay in this instance, but I wouldn't want to risk it.) But this is true for any RAID, which is why many controllers come with a BBU (and if you don't have a BBU on your hardware RAID controller, then you absolutely need the UPS setup I described). OTOH, the OP wasn't clear on what he was doing; perhaps he is just playing around, and doesn't care about data preservation at this time. If you're just testing performance then data integrity in the face of a power failure is less of a concern. --keith A UPS is certainly better than nothing, but I would not consider it safe enough. A BBU/FBU will protect you if the node loses power, right up to the failure of the PSU(s). I've seen shorted cable harnesses taking out servers with redundant power supplies, popped breakers in PDUs/UPSes, knocked out power cords, etc. So a UPS is not a silver-bullet to safe write-back caching in software arrays. Good, yes, but not perfect. This is a pretty interesting discussion but has not revealed an on-line tutorial. Anyone? Dave -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos -- We hang petty thieves and appoint great ones to office -- Aesop ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
Raid only protects against one specific sort of failure, where an entire disk drive fails. It doesn't protect against data corruption, or system failure, or software failure or any other catastrophes. +1 Try ZFS http://zfsonlinux.org/ ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
A UPS is certainly better than nothing, Unless your using ZFS then nothing is perfectly ok. ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
[CentOS] Centos 7 RAID tutorial?
I want to set up a new CentOS install using version 7 and would like to experiment with various RAID levels. Anyone care to point out a tutorial? TIA Dave -- We hang petty thieves and appoint great ones to office -- Aesop ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 9/7/2014 7:19 PM, Dave Stevens wrote: I want to set up a new CentOS install using version 7 and would like to experiment with various RAID levels. Anyone care to point out a tutorial? how many drives do you have for this experiment? whats the target usecase for the file systems on the raid(s)? whats the level of data resiliance required by said use case? Raid only protects against one specific sort of failure, where an entire disk drive fails. It doesn't protect against data corruption, or system failure, or software failure or any other catastrophes. -- john r pierce 37N 122W somewhere on the middle of the left coast ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On Sun, September 7, 2014 9:30 pm, John R Pierce wrote: On 9/7/2014 7:19 PM, Dave Stevens wrote: I want to set up a new CentOS install using version 7 and would like to experiment with various RAID levels. Anyone care to point out a tutorial? how many drives do you have for this experiment? whats the target usecase for the file systems on the raid(s)? whats the level of data resiliance required by said use case? Raid only protects against one specific sort of failure, where an entire disk drive fails. It doesn't protect against data corruption, or system failure, Even more: system failure or power loss is more likely to destroy all data on software RAID than on a single drive when there is a lot of IO present (to the best of my understanding, loss of cache software RAID is using is more catastrophic compared to journaled filesystem under same circumstances - somebody may correct me). So, there may be worth thinking about hardware RAID. Just my 2c. Valeri or software failure or any other catastrophes. -- john r pierce 37N 122W somewhere on the middle of the left coast ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos Valeri Galtsev Sr System Administrator Department of Astronomy and Astrophysics Kavli Institute for Cosmological Physics University of Chicago Phone: 773-702-4247 ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 2014-09-08, Valeri Galtsev galt...@kicp.uchicago.edu wrote: Even more: system failure or power loss is more likely to destroy all data on software RAID than on a single drive when there is a lot of IO present (to the best of my understanding, loss of cache software RAID is using is more catastrophic compared to journaled filesystem under same circumstances - somebody may correct me). So, there may be worth thinking about hardware RAID. I think an essential feature of any md RAID that's not a RAID1 is a UPS and a mechanism for a clean shutdown in case of extended power failure. (An md RAID1 might be okay in this instance, but I wouldn't want to risk it.) But this is true for any RAID, which is why many controllers come with a BBU (and if you don't have a BBU on your hardware RAID controller, then you absolutely need the UPS setup I described). OTOH, the OP wasn't clear on what he was doing; perhaps he is just playing around, and doesn't care about data preservation at this time. If you're just testing performance then data integrity in the face of a power failure is less of a concern. --keith --keith -- kkel...@wombat.san-francisco.ca.us ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 07/09/14 10:43 PM, Valeri Galtsev wrote: On Sun, September 7, 2014 9:30 pm, John R Pierce wrote: On 9/7/2014 7:19 PM, Dave Stevens wrote: I want to set up a new CentOS install using version 7 and would like to experiment with various RAID levels. Anyone care to point out a tutorial? how many drives do you have for this experiment? whats the target usecase for the file systems on the raid(s)? whats the level of data resiliance required by said use case? Raid only protects against one specific sort of failure, where an entire disk drive fails. It doesn't protect against data corruption, or system failure, Even more: system failure or power loss is more likely to destroy all data on software RAID than on a single drive when there is a lot of IO present (to the best of my understanding, loss of cache software RAID is using is more catastrophic compared to journaled filesystem under same circumstances - somebody may correct me). So, there may be worth thinking about hardware RAID. Just my 2c. Valeri Valeri makes an excellent point, which I would like to elaborate on; Hardware RAID *with* flash-backed/battery-backed cache. I find it endlessly fascinating how many machines out there have hardware RAID with BBU/FBU. When using write-back caching without a battery leaves you in no better position. Note that if you do get hardware RAID with BBU/FBU, be sure the cache policy is set to Write-Back with BBU (or your controllers wording). The idea here is that, if the battery/caps fail/drain, the controller switches to write-through (no) caching. I'm not so familiar with software RAID, but I would be surprised if there isn't a way to force write-through caching. If this is possible, then Valeri's concern can be addressed (at the cost of performance). digimer -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Centos 7 RAID tutorial?
On 07/09/14 11:01 PM, Keith Keller wrote: On 2014-09-08, Valeri Galtsev galt...@kicp.uchicago.edu wrote: Even more: system failure or power loss is more likely to destroy all data on software RAID than on a single drive when there is a lot of IO present (to the best of my understanding, loss of cache software RAID is using is more catastrophic compared to journaled filesystem under same circumstances - somebody may correct me). So, there may be worth thinking about hardware RAID. I think an essential feature of any md RAID that's not a RAID1 is a UPS and a mechanism for a clean shutdown in case of extended power failure. (An md RAID1 might be okay in this instance, but I wouldn't want to risk it.) But this is true for any RAID, which is why many controllers come with a BBU (and if you don't have a BBU on your hardware RAID controller, then you absolutely need the UPS setup I described). OTOH, the OP wasn't clear on what he was doing; perhaps he is just playing around, and doesn't care about data preservation at this time. If you're just testing performance then data integrity in the face of a power failure is less of a concern. --keith A UPS is certainly better than nothing, but I would not consider it safe enough. A BBU/FBU will protect you if the node loses power, right up to the failure of the PSU(s). I've seen shorted cable harnesses taking out servers with redundant power supplies, popped breakers in PDUs/UPSes, knocked out power cords, etc. So a UPS is not a silver-bullet to safe write-back caching in software arrays. Good, yes, but not perfect. -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
