How about just not partitioning the whole disk of the
larger disks? Note I didn't come up with that idea, that came from a young
whippersnapper I know out of Redmond whom I was discussing the fastest AD disk
configs with a few weeks ago. I haven't tried it but it makes sense to me.
Just allocate maybe 10-12GB of each of the 36GB drives across an array or
so.
Course you could always say screw the fault tolerant
RAIDs, this isn't Exchange, and run commando with a stripe set. If you have
enough extra DC capacity in the site you could have them all running really
fast and then when one blows it just goes away. Most applications that are
written properly for AD handle that just fine except apps that hard sync to a
single DC.
If I have 7-8 disks, I wouldn't hesitate to put them in a
single RAID-10/0+1 type config. OS and Logs are snoring on most DCs. All of
the action is around the DIT unless you get that baby into memory which was
the first I think 20 responses I got from the whippersnapper. Use 64 bit. I
know but... use 64 bit... I know but.... use 64 bit.... I know but.... are you
still here, use 64 bit....
joe
We have allot of users coming back to our central site
and we use the following config.
adapter #1 ====> raid 1 ( 2 disk)
O/S
adapter #2 ====>raid 1 ( 2 disk) AD
LOGS
adapter #3 ===> raid 5 (3 disk) with
global hot spare AD Data
the key to this using this is that all the equipment
(SCSI disk,SCSI controller) is Ultra 320 spec with low latency and low seek
times (15 K rpm usually). The other thing that has been
noticed is that use as small a disk as you can get. (8 GB)
Some of the manufacturers are saying they only can supply 36GB drives on new
equipment. These drive are ok but the seek time goes up because of
the size of the drive
this config works good also
adapter #1 ====> raid 1 ( 2 disk)
O/S
adapter #2 ====>raid 1 ( 2 disk) AD
LOGS and raid 5 (3 disk) with global hot
spare (total of 6 on this channel)
hope this
helps
From:
[EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of joe
Sent: Sunday, November 06, 2005 11:12
AM
To: ActiveDir@mail.activedir.org
Subject: RE:
[ActiveDir] Raid suggestions for DC maybe OT
LOL. I actually pinged Rick on the "official" guidelines
previously for an Enterprise class DC with 4 disks, he was actually one of 4
people I queried since I hadn't seen what I considered good official docs on
it. Rick quoted the K3 Deployment guide which is definitely a good start. It
indicates
RAID 1 - OS
RAID 1 - Logs
RAID 1 or 0+1 - SYSVOL/DIT
If you have less than 1000 users using the DC it says you
can use one single RAID-1 for the whole thing. Though you have the same issue
here as you have for anything, how are the 1000 users using it and what else
is using it? Exchange? If so, I doubt I would do a single RAID-1 unless it was
very few users.
Otherwise you are looking at a minimum of 6 disks for all
RAID-1s or 8 disks if 0+1 and RAID-1.
When you actually look at it, the OS and the logs are
using little IOPS on a dedicated DC and splitting them off onto their own
"disk" is probably unneccessary. The DIT assuming it isn't all cached and is
being heavily hit (like say by Exchange) is raping the disk subsystem. When
you have an app that wants lots of IOPS what do you? You increase the number
of spindles... So for throughput, the fastest four disk
configuration is going to be a RAID-5 or a 0+1 or 10. In tests I did
several years ago with one hardware vendor RAID-10 and 5 were very close
(within a few IOPS) with RAID-5 eeking out the lead. They both blew
RAID-1 away. In more recent tests I heard of from someone using another
hardware vendor, RAID 0+1 eeked out over RAID-5 by a few IOPS and again
blew RAID-1 out of the water. Obviously the tests were different so I
recommend folks do their own testing with their own hardware. The fastest disk
configs I am aware of are 6 and 8 disk RAID-10/0+1 setups with 8 disks
supposedly being rock star fast if you have the room internally. To put it
another way, if I had 8 disks, I certainly wouldn't be following the
deployment guide config for those disks, it would be a RAID-10/0+1 setup. The
6 disk RAID-10s (The Dells I was using then didn't support 0+1) I built about
3 or 4 years ago were screaming fast compared to everything else at the time I
had worked with. Now I don't do anything with hardware, I am more cerebral.
;o)
And note, obviously I am not talking software RAID, this
is all hardware. Software RAID isn't something you use for production machines
IMO.
joe
Dan - there will likely be as many opinions on this topic
on this list as there are knots on joe's head.
Basic rules for a DC are this (IMHO):
Mirrored (or RAID1) for OS
Mirrored (or RAID1) for DIT and Logs
You can certainly host a third mirrored pair for the
logs, but that will mostly depend upon how BUSY your AD is and how high the
replication traffic, changes, updates etc. that you
experience.
If you're asking this, you most likely have a newer AD,
or are re-architecting. In either case, I'd start with the above and
then monitor the performance with PerfMon. Make some decisions on
whether to ADD the third mirror based upon the I/O and performance impact of
log writes vs. impact on the database reads/writes.
Hope this helps!
Rick [msft]
--
Posting is provided "AS IS", and confers no rights or
warranties ...
What would be the suggested RAID and partitioning
scheme for a Domain controller.
Any suggestions are
appreciated.
Thanks.
Dan Cox