What were the support reasons? Someone whined until they got the OS on
RAID-1 because that is the way "everyone" says they should do it or
another
popular one is that is the way we "always" do it?
One of the issues is that most of the machines folks like to make into DCs
just don't have enough disk slots to have multiple spindles for the DIT if
you take up 4 for the OS and Logs. If you can get away with
mirror/mirror/6
disk 0+1/10... Excellent, especially if x64 with sufficient RAM. If the
disk
counters start to show queuing on the DIT drive greater than what I
consider
heavy load (~2x#spindles) though I wouldn't hesistate to tear that down
and
make it into a single 10 disk RAID 0+1/10/5. With x64, as Paul indicated,
that generally shouldn't happen though unless you don't have enough memory
or possibly you have recently rebooted and are defrosting the cache.
Mostly though, people should be looking at their own perf counters and
figuring out what they should be doing. Pay especially close attention to
Exchange GCs during the "morning rush" and the after lunch "rush", those
are
the two areas that tend to initially start showing pain.
joe
--
O'Reilly Active Directory Third Edition -
http://www.joeware.net/win/ad3e.htm
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Paul Williams
Sent: Tuesday, October 17, 2006 5:03 AM
To: ActiveDir@mail.activedir.org
Subject: Re: [ActiveDir] Seperating Database and logs on seperate disks
Having discussed this quite a lot recently, I'll give you all an insight
into how I wanted to do it and how we are doing it (support reasons caused
me to be overridden):
[want] 6 disks in a RAID10 array, with three volumes: OS, DIT & Logs,
SYSVOL
and Scratch area.
[reallity] 2 disks in a RAID1 array for OS; 4 disks in a RAID10 array for
DIT & Logs, with another volume for SYSVOL and scratch.
Scratch contains the IFM directory (temporarily) and perf logs, etc.
I agree with Joe 100% (probably because we have discussed this offline in
depth and he has moulded my opinions <g> ). Smaller environments don't
need
to worry about it. Big environments need to think about it. Although, as
Joe mentions, it's rare you'll need much space for the log files. Even if
you provision a couple of hundred thousand users (which takes an hour or
two) you don't need much space for logs. Which is why I hate the 3x RAID1
idea that is out there. Disks are cheap for sure, but that's still a
serious waste of two disks where they could be put to use for the DIT,
which
is being slammed with read requests.
Also remember that in smaller environments, or medium-sized environments
that have didicated DCs, a DL360 (or equivalent) which only has room for
two
local disks, will happily run as a DC. A couple of the smaller projects
I've worked on in the past (~7,000 users) we used just this. Although in
some of those we had to use DL380s at some of the branches as they were
also
running Exchange! : (
One other thing I'd like to say here, is if you do need to worry about
separating your disks, then you really should be looking at x64. You get
better throughput with x64 on disk and memory access, and you also have
the
ability to get all, or at least a chunk of, your DIT data (as in objects
that matter to your and your queries) into RAM. Those disk specs above
are
being implemented with x64 dual-core, dual-proc systems with 32GB of RAM
as
our standard DCs.
(What can I say, I have a reasonable sized DIT ;-)
(or so I'm told...)
--Paul
----- Original Message -----
From: "joe" <[EMAIL PROTECTED]>
To: <ActiveDir@mail.activedir.org>
Sent: Tuesday, October 17, 2006 5:36 AM
Subject: RE: [ActiveDir] Seperating Database and logs on seperate disks
I am surprised there aren't more responses to this.
My personal opinion is that a vast majority of installations don't need
to
separate off the logs for perf. In fact, I have often recommended running
everything on a single RAID 0+1/10/5 (partition logically if you want to
say
separate off the OS and the AD stuff) to get better perf than splitting
logs
and OS off onto their own disks. Especially in larger orgs for Exchange
GCs
that tried to follow the deployment docs and do mirror, mirror, mirror or
mirror, mirror, 0+1 but didn't have enough disks to get a good 0+1.
In every case that I have had to review DCs with questionable disk
subsystem
perf, the issues are always around the DIT while the disks for the OS and
the Logs are snoozing with IOPS sitting there not being used that could
have
saved the DIT from getting sucked into the mud. Rebuilding the disk
subsystem with all disks in one of the above configurations has
alleviated
the issues in every case. Whether RAID 5 or 0+1/10 is faster you will
want
to test with your own disk subystems (say with IOMETER), it seems to
vary.
I
have seen RAID-5 faster and I have seen on different machines 0+1/10
faster.
A case I am aware of where the logs definitely were good off on their own
and would have seriously impacted perf if they weren't was Eric's DIT
experiment where he built a 2TB DIT but he was adding objects at a very
high
rate of speed constantly for quite a while so the logs were being beaten
pretty well.
joe
--
O'Reilly Active Directory Third Edition -
http://www.joeware.net/win/ad3e.htm
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of AD
Sent: Monday, October 16, 2006 11:29 AM
To: ActiveDir@mail.activedir.org
Subject: [ActiveDir] Seperating Database and logs on seperate disks
Is there any other reason other then performance to have the Active
Directory log files and database on separate disks?
Opinions are welcome.
Thanks
Yves
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