Disk alignment questions with Esx 4

[evolmar]

Hi all,

I want to begin by saying I apologize in advance if this has been posted numerous times. I've tried numerous searches in here and google and the various white papers to no avail.

We have a Clariion CX3-40 and have mapped a 525GB LUN to our very first production ESX host. The host has ESX 4 installed.

Within the host I see the LUN and have formatted it with VMFS with 8 meg block size. All is well until I I realized I have to address alignment concerns. When one used the VI client to create the datastore,does vSphere automatically handle the disk alignment for you? What about guest OSes?

Also regarding the 8 meg block size. I read here that using 8 meg block size right off the bat is the way to go. True?

Thanks in advance for all of your guidance.

Regards,

e

[Troy_Clavell]

If you add the storage via the vSphere Client the alignment of your datastores will be done correctly

As for the guests, you may want to look at this .pdf

http://www.vmware.com/pdf/esx3_partition_align.pdf

It can be debated as to whether or not disk alignment of your guest actually works. I guess it's up to you to decide.

Below is another great post on 8MB Block sizes you may want to take a look at.

http://www.yellow-bricks.com/2009/03/24/an-8mb-vmfs-blocksize-doesnt-increase-performance/

[davidbarclay]

>does vSphere automatically handle the disk alignment for you

Correct, if created using the VI Client. Same applies in VI3.

>What about guest OSes?

No, the VI Client has nothing to do with this.Depending on the OS you are installing, the procedure is different, or not required. e.g. Windows 2008 is aligned by default. Windows 2003 requires the disk be aligned with winpe first (see the VMware PDF here).

As for Troy's comments about disk alignment, I'm not sure I agree. I agree you should test yourself, but it's pretty clear what is technically acheived. It may be of little significance in your environment..but in larger more complex environments it certainly does IMHO.

>regarding the 8 meg block size

I completely agree with this approach. Troy's comments focus on performance...but that's not the only point. I see 8MB blocksize as the most flexibility, without sacrifice (performance or otherwise).

Dave

[Troy_Clavell]

As for Troy's comments about disk alignment, I'm not sure I agree. I agree you should test yourself, but it's pretty clear what is technically acheived. It may be of little significance in your environment..but in larger more complex environments it certainly does IMHO.

Just so you know, I am 100% for alignment of the guests. But rather then sparking a debate on whether or not you will see better I/O, I just left it to the OP to decide or have other chime in on their expierences.

[davidbarclay]

Fair enough. I'd just rather see people standardise on it...then worry about how to fix 100+ guests later on.

Dave

[evolmar]

Thanks for your help guys! Much appreciated! :smileyblush: