iSCSI San configuration for ESX 3.5

[bundaburg1]

Hi

Just a bit of background on what i'm trying to do:

We have 2 x Dell R900's with a PS5000 iSCSI SAN (with 8 300gb 15k ), each server will be running 3-4 RHEL VM's with between 8-16 gb ram and approximately 600gb of disk between them.

There is going to be 1 MySql staging database.

What would be best practise for the SAN configuration? My thoughts were from reading here is having 4smaller LUNS of about 150gb (Raid5) for the 'general' servers and a single Raid10 LUN for the database server partition.

Any input greatly appreciated, thanks.

[matuscak]

The Equallogic arrays require that the entire box be formatted one way, so If you have a single PS5000, you're not going to be able to have some volumes be RAID 10 and some be 50 (or 5). I think you'll find that Equallogic doesn't really advocate using RAID 5 due to rebuild time issues. I suppose it's also worth mentioning that the newly announced version of the EQL firmware supports RAID 6 as well.

As far as dividing up the volumes, I personally tend have a volume per production VM (thin provisioned). We've got a larger shared volume where test machines, templates, ISOs and so on live.

[kjb007]

One large volume will not be very efficient in terms of I/O. With regard to performance, smaller volumes perform better than larger ones as I/O is distributed. If you create one large RAID5 volume, your resultant volume will be greater than ESX will allow, so that's not the best way to go. I would instead create 3-4 RAID5 volumes for performance, but you would lose a lot of disk that way, depending on how your storage will allow you to group your disks.

The general rule is to use smaller LUNs. Unless you have a very high transactional db, the disk cost for RAID10 will probably not be worth the performance benefit.

-KjB

VMware vExpert