SAN - Disk Configuration

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SAN - Disk Configuration

Dave Klug

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March 2, 2010 at 7:42 am

#386416

I'm currently in the process of creating a database cluster and am having a hard time finding best practices for configuring the LUNs for the databases. I'm going to have separate drives for Data, Log and TempDB but the SAN guys are telling me just give them the drive size and the SAN will do the rest. My concern is the LUNs will be actually overlapping the disks and IOps may suffer as a result. Does anyone have any experience with a HP EVA 4000 SAN and can give me some guidance on how the LUNs should be created.

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Roy Ernest SSC-Dedicated Points: 38780 More actions · Answer 1

I have some experience with HP EVA SAN but not the good kind. Our DB was clustered on a HP EVA SAN. We lost the SAN and the HP people could not figure out why we lost it... :hehe:

Thank God we had a warm stand by set up as well with DAS.

-Roy

Dave Klug SSCertifiable Points: 5811 More actions · Answer 2

I have a cluster currently on this SAN and see high disk queue lengths when ETL jobs are running through. I don't really trust the SAN admin to tell me it's configured as it goes against a presentation I saw at PASS for best practices. It may be I have no control on the HP EVA but prefer to get some kind of confirmation on that.

ClusterJunkie Old Hand Points: 385 More actions · Answer 3

Let me guess, the SAN admins also said to not worry about RAID 1, RAID 5, RAID 10 etc - since its a high speed SAN it does not matter?

Don't believe a word of it...

If you do a search for best practises for SQL on HP SANS, you should be able to find out some useful whitepapers on optimal configuration. I have so

for an EMC clarion SAN to good effect.

Also, pay particular attention to misaligned partitions. Misconfiguring could slice 20% off you're SQL performance. They're is an excellent ppt floating about

written by Jimmy May. Recommend highly.

Dave Klug SSCertifiable Points: 5811 More actions · Answer 4

I just got a response from the vendor nad here's what he says. He is recommending proper RAID levels and the disk alignment was something I've already got on my list.

The EVA is not like a standard Disk array, all disks are grouped into a pool (a single pool is recommended by HP), from the storage pool, vDisks are created this is the LUN that is presented to the host. The LUN is where you can pick which Raid level you want. So for maximum performance for SQL you would want to have your transaction logs on a vRAID 10, and you actual databases RAID 5, unless the database is mainly writing. If your database environments is standard vRaid 5 would be fine. The great thing about the EVA is you get the performance of all spinals instead of a fixed set of say 6 or 8. This allows the EVA to provide better performance. The vDisks are created across all disks.

Steve Jones - SSC Editor SSC Guru Points: 736212 More actions · Answer 5

We had an HP years ago with the same recommendation. For some instances it was fine, for some it was an issue. If you have heavy I/O, this can be a problem. Despite what the vendor says, they are counting on a distribution of I/O that is spread for this to work.

Dave Klug SSCertifiable Points: 5811 More actions · Answer 6

Do you have an alternate recommendation on how to configure the SAN?

Roy Ernest SSC-Dedicated Points: 38780 More actions · Answer 7

Like ClusterJunkie said.. Read jimmy Mays Blog. He is a brilliant guy. You will get quite a bit of Info. Here is one of the blogs he has written about this.

http://blogs.msdn.com/jimmymay/archive/2009/05/08/disk-partition-alignment-sector-alignment-make-the-case-with-this-template.aspx

-Roy

Andeavour SSCrazy Points: 2600 More actions · Answer 8

We're having some major performance issues with a NetApp SAN, both with throughput on the controllers and with performance of the disks in the various aggregates.

I've been over it several times and raised the matter of alignment in countless meetings, but the general opinion is that the NetApp LUN provisioning software takes care of this, and I can't convince anybody to actually check it to make sure it does. (I don't have the access to do it myself).

I'm sure we shouldn't be seeing the contention issues we do within the aggregates, and I'm not satisfied that this couldn't be down to alignment, but I find myself running up against "SAN knows best" at every turn.

Dave Klug SSCertifiable Points: 5811 More actions · Answer 9

That's the fear I have now... just trust the SAN and everything will be fine.

ClusterJunkie Old Hand Points: 385 More actions · Answer 10

Upgrade to W2k8, it sorts the alignment within the 0S ;-0

ClusterJunkie Old Hand Points: 385 More actions · Answer 11

Upgrade to W2k8, it sorts the alignment within the 0S...apparently ;-0

Dave Klug SSCertifiable Points: 5811 More actions · Answer 12

That we are doing. Will it also take care of the sector alignment on the LUNs?

Chuck Hottle SSCarpal Tunnel Points: 4777 More actions · Answer 13

I'd be very interested in hearing more about the NetApp issues that the one person (Andeavor) mentioned. Our Infrastructure group is considering NetApp and I have concerns about the LUN provisioning for a SQL Server environment.