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SQL Virtualization - SAN setup

hi all

we will soon be virtualizing our SQL server using vmware and moving it to a SAN.

what i am worried about is configuring the virtualisation wrong so that the SAN disc subsystem is not utilised properly.

what i will be doing is breaking the 12 physical discs into 4 logical drives

c: 2 discs -raid 1 - os
D: 6 discs - raid 5 - databases
E 2 discs - raid 1 - logs
F 2 discs - raid 1 - Tempdb

regarding disc's D,E and F, do i simply map these to drive C. as i assume if these discs are setup as virtual drives the virtual machines disks are simply files stored on the file system and i will lose the benefit of the Raid setup?

can someone advise? all advice appreciated!

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Alex Galbraith

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malraff

ASKER

hi jkagalbraith

thanks for your input,
there wil be no other machine on the san, so if i go with option A - would i lose much performance?

and considering i have 12 * 300k 15rpm discs, do you think i am spliting them wisely with best raid selection for each?

i was tempted to go raid 10 for the databases, but decieded not mainly due to the fact iv never configured a system as such and read that some raid controller really do not like it?

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coolsport00

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malraff

ASKER

cheers coolsport, good to hear someone thinks im on the right track !

Alex Galbraith

I have just replied to someone regarding choice of RAID 5/10 here:

https://www.experts-exchange.com/questions/25753270/VMWare-ESX-4-0-RAID-5-vs-RAID-10.html

RAID10 will give better write performance at a greater overall cost.

If you have no intention to be able to use VMotion then the RDMs will give you better performance, however, unless your server is being completely hammered, the performance hit of full VMFS virtualisation will be minimal to the point where you will not likely tell the difference.

coolsport00

You can use VMotion with RDM...just VMotioned 3 servers that have RDMs associated with them.

~coolsport00

Alex Galbraith

It does work, but its flakey at best and wont work if you have clustered VMs (not technically supported anyway).

coolsport00

Hmm..It's worked for me, unhindered, for the past 2yrs; agree about the cluster, though.

~coolsport00

malraff

ASKER

jkagalbraith: and regarding info iv read with some controller issues with raid 10 is that mostly uncommon now?
also does raid 10 only workin multiples of 4? eg i have 6 discs for the databases, but i dont see how raid 10 would utilise all
and would a 6 discs raid 5 be similar in speed to 4 disc raid 10? or is that a pointless comparison?

bbnp2006

Yes, you won't have any problem creating a RAID10 with 6 disks. It will be configured as a mirror of 2 sets of 3 disk in each set. For performance comparison between 6 disk RAID 10 and 4 disk RAID 5, i would say you won't see too much difference, but the more underlying disks you have, the faster the write/read operation generally will be.

Alex Galbraith

for 6 (RAID10) v 4 (RAID5) you will see a bit faster writes on RAID10, and obviously the RAID10 will provide better redundancy (minimum 2 disks can be lost and no data loss).

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BigSchmuh

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malraff

ASKER

ok..

alot of info to digest, BigSchmuh> i do have a gut feeling raid 10 may be the way to go, i do have a week to test so i guess i can try a few configs first!