Spindles do mean drives
For SQL VMs disk I/O setup is just as important as on a physical system.
I posted about this here last night
You really should take a look at this whitepaper which covers SQL I/O setup and Best practices
Also MSFTs take on it
As you do not have Shared storage your options are a little limited at this time but setting up the I/O subsystem on a SQL system (Physical or Virtual) is something you want to put some thought into or you will face performance issues and unusual bugs down the line.
What are RDMs?
Just having a look through a couple of them documents. I was reading them yesterday evening.
Are you guys saying that regardless of the physcal infrastructure (say
raid 5 or 10) i should still set my VMs up with 3 seperate disks
(system, logs and data) regardless of the underlying hardware.
Thanks for the advice - much appreciated
RDM = Raw Device Mapping
These are LUNS presented from shared storage more or less directly to the VM.
As you do not have shared storage you need not concern yourself with them right now
As to point 2 yes separate system/boot, data and logs (While your at it you could isolate tempdb on separate vmdk, although that might be a bit much)
If not for performance this will at least make a future migration to an RDM a little less difficult.
If you are using direct attached storage right now I would setup the drives as you would in a psyhical server. One thing to remeber when you go virtual is you want to keep the same proven practices that would of been setup on a psyhical system. When you have shared storage you would want to use RAW LUN mappings for the SQL server but since you have direct attached storage I would break up your raid sets into raid 10 (1+0).
Essentially create a raid 10 set of disks for your database, and another raid 10 set for your transaction logs. The OS could be on a mirror if you like as it doesn't require as much perfomance but it is up to you. I would do this for each SQL server. So your setup would look something like this:
Raid 1 Mirror (2 disks) - Datastore for OS's - virtual disk for your os
Raid 10 - (4, or 8 disks) Datastore for SQL database - virutal disks for your SQL database
Riad 10 ( 4 or 8 disk) - Datastore for SQL Transaction Logs - virutal disks for your SQL transaction logs
I hope this helps, if you have any questions let me know.
I would also give a listen to Podcast #32 of the VMware COmmunities Roundtable Podcast. This discusses this in some detail but the long and short of it is, what you do in the physical world translate into the virtual world. If you would normally use multiple disks then you would continue to do so, but remember multiple VMDKs on the same LUN does not map to multiple disks in the physical world you would have to have multiple VMDKs each ondifferent LUNs or using RDMS to get that.
Edward L. Haletky
VMware Communities User Moderator
Author of the book 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', Copyright 2008 Pearson Education.
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