Placement of guest os/data disks

[ShawnPD]

I am sure this question has been answered before, however I have not found an answer yet...we are setting up a new vm on an esxi 4.0 host. We are using the software iSCSI initiator. Our customer has requested we place the os drive on one Lun and the data drive on another lun. His rationale is this will allow for better performance. Our team's rationale is since this both LUNs are on the same aggregate; performance will not be greatly increased. Also, it this may make general housekeeping less efficient.

Is there a best practice concerning the placement of the vmdks? I did some Google searches and couldn't really find an unequivocal answer.

[a_p_]

Depending on the SAN it may make sense for e.g. an SQL server to put the DB's and the transaction logs on different LUNs. However IMO there's no benefit in separating the OS and the data disks, because the OS usually does not have a high IO (reads/writes).

André

[Texiwill]

Hello,

If the LUNs are both using the same path to the array then the only win is that you have more IO Queues available within the stack. This is why Queudepth is a pretty major factor with FC HBAs. Other than there is no major win if the LUNs are using the same wire. However, if they are load balanced across multiple wires, then yes there is a chance for improvement.

It really depends on your networking setup for iSCSI. Aggregate means many things, and since ESX by default does not 'aggregate' traffic but load balances, you need to know on which wire the LUN is writing/reading......

Best regards,
Edward L. Haletky VMware Communities User Moderator, VMware vExpert 2009, 2010

Now Available: 'VMware vSphere(TM) and Virtual Infrastructure Security'[/url]

Also available 'VMWare ESX Server in the Enterprise'[/url]

Blogging: The Virtualization Practice[/url]|Blue Gears[/url]|TechTarget[/url]|Network World[/url]

Podcast: Virtualization Security Round Table Podcast[/url]|Twitter: Texiwll[/url]