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SBS 2011 and RAID 10

juli asked
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Last Modified: 2016-12-08
I know there is a lot of debate on the issue of RAID and putting OS on its own array.

I'm currently considering the purchase of a Dell T410, 24GB RAM, 6 250GB  SATA Drives and X5660 processor.    Getting SBS 2011 for about 25 users (no SQL needed)

I have one consultant who recommends RAID 1 for OS and RAID 5 for remaining 4 drives.
I have another consultant recommending RAID5 alone (performance)

I also see a lot of recommendations online for RAID 10.    

Does anyone have an opinion on how SBS 2011 will do with RAID 10 (OS & Data on different partitions but same array)?  I think we can afford to give up 50% of the disk space if its worth it.

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Philip ElderTechnical Architect - HA/Compute/Storage

Hardware RAID Controller PERC 6/i + Battery Backup.
Use 15K SAS drives instead of SATA. SATA has its issues, even the Enterprise grade ones.

For example:
 5x 300GB 15K SAS drives configured in RAID 5 (1.2TB available).
 1x 300GB 15K SAS drive as hot spare.

The above configuration would give awesome read across the five spindles while writes would be quite good.

It is important to note that Exchange 2010 is completely different in its needs versus SBS 2008 and Exchange 2007. E2007 was very disk intensive while E2010 wants to saddle everything into RAM. The goal for E2010 was to run a whole lot of user mailboxes on one SATA drive with it being met with flying colours.

That being said, I/O for all other needs will always be the biggest consideration when configuring a server.

We stopped using SATA in servers a couple of years ago due to reliability concerns (check Dell's SATA warranty), drive signalling/communication issues with the RAID controller, and overall lackluster performance.

SAS was and is designed to run in a server setup. SAS drives, in our experience, run faster and with way more reliability than SATA.


Thats all well and good but 6 300GB SAS drives are going to set you back a lot more than 6 SATA Drives and if you read his requirements its only for 25 Users for exchange so there is no need for the high performing SAS Drives.

As for Raid 5 it is just rubbish, you're right in saying he'll have very quick read access because it will be able to read from 5 or 6 drives at once but when you try to write to the disk it has to calculate and write the parity data which really cripples the setup.

Raid 10 also allows you to read from all six drives at once and when writing to the drives it is the equivalent of 3 drives in a Raid 0 which will always blow Raid 5 out of the water.

I would even go as far as saying that a Raid 10 of 7500 RPM SATA Drives will out perform a Raid 5 of 15000 RPM SAS Drives in terms of write performance.
Philip ElderTechnical Architect - HA/Compute/Storage

Hardware RAID controllers that utilize battery for the cache can be set into Write-Back mode. This allows the RoC to calculate all of the necessary parity bits on the fly and write only what is needed.

More spindles is always better for RAID 5.

RAID 10 does not read all six since there are three _mirrored_ pairs. Effectively this is a three spindle stripe due to the mirror.

So, a 5 spindle RAID 5 will read 5 spindles while a 3 spindle RAID 10 (six drives) will only read three. In our extensive testing of the various setups, more spindles always means more I/O throughput.

In our testing SAS has consistently out performed SATA.


Thats all well and good but you are incorrect about not reading from six spindles.

If you have a Raid 1 configuration data can be read from both drives at once since they both contain the same data. However when data is written it is only as fast as writing to one drive.

If you have Raid 0 data is striped across all 3 drives so data can be written to 3 drives simultaneously and read from them simultaneously.

So if you have Raid 10 (Raid 1+0) you can read from all six drives at once and write to 3 drives at once.

In comparison with Raid 5 yes you are striping your data across all drives when writing so you can write to 5 drives at once, in theory this seems good however in practice the performance is rubbish. It doesn't matter if you have battery backup and write-back mode enabled. The time taken to calculate the parity bits will always be holding you back.
Philip ElderTechnical Architect - HA/Compute/Storage

In your read example for RAID 10 ... it sounds like the definition for RAID 0, that is the read is pulled from all six spindles.


Shall we agree to disagree?



I think the performance really comes down to how much cache you have on your controller. If your Raid 5 Controller has plenty of cache you'll probably not notice anything but once you try to Write large files over a GB or so you'll notice it.

Plus what happens when a drive dies in Raid 5, you better hope your server isn't busy because for the time it takes to rebuild the array your system will run at around 50% performance. Raid 10 is a lot better at recovering from failed drives.


Well,for cost reasons I need to stick with SATA - especially if I'm considering RAID 10.
The other option I'm considering is RAID 5 with hotspare.

We were going with a H700 RAID Controller w/ 512MB cache.

I really wanted to make sure that I wasn't making a mistake with RAID 10 and performance for SBS 2011 - considering Exchanges 2010 requirements.
Josiah RockeNetwork & Communications

MPECSInc, based on your SBS setup guide, I am halfway through a setup of our new SBS 2011 server on RAID 10. Are you recommending I change that? We got the H700 w/512MB cache (write-back might not be enabled...have to check that). Also have 12x300 10k 2.5" SAS. (2 in Raid 1 for host OS, 1 stand alone for host swap file, 8 in RAID 10 for SBS 2011 in Hyper-V, and 1 global host spare)..

Please advise!
Philip ElderTechnical Architect - HA/Compute/Storage

No, not necesarily at this point. The jury is still out for larger deploys (above 8-10 seats).

We were big on RAID 10 with SBS 2008 because of Exchange's big I/O needs along with everything else going on with SBS 2008.

We are still testing out our SBS 2011 configurations via in-house and client deployments to fine tune our configurations going forward.

RAID 10 will _always_ give the best overall R/Wr performance. This configuration has been the number one array structure for high I/O database and e-mail servers for a very long time.

The advent of better overall performance for RAID 5 is relatively recent due to technology improvements both in drives and RAID controllers (including cache abilities).

So, for smaller 5-8 seat setups where the OS is on a physical server we are in the process of testing 4-6 spindle (Always 15K SAS) RAID 5 with battery backup or SSD Cache (Intel/LSi feature). Things are looking very promising.

Please keep in mind that we faced some real performance struggles early in the life of SBS 08 where SATA and on board RAID were used for RAID 5 configurations. This particular setup was causing backup failures because the required I/O between OS/Exchange and WSB for VSS snapshots was just not there. This is the primary area for our testing at this point (I/O for day-to-day + VSS snapshot activities).

Josiah RockeNetwork & Communications

Ah. Well, I follow your blogs, so I'll be looking for updates. Thanks for the quick reply!
Philip ElderTechnical Architect - HA/Compute/Storage

You are welcome. :)

Philip ElderTechnical Architect - HA/Compute/Storage

JRockman, BTW after looking at your configuration question things look really good.

Virtualizing OSs on an host changings things dramatically. We have lots of posts on that too. RAID 10 would be our mainstay for the entire spindle set with a small partition for the host OS at the beginning of the LD.

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