VMware Storage Tidbits

VMware Storage Tidbits

When researching the interaction of storage and VMware for my upcoming TechTarget seminar series on storage virtualization , I picked up a few little tidbits of information that I wanted to share...
Beware of block sizes greater than 256 KB when using certain Fibre Channel arrays! [VMware's performance research | http://www.vmware.com/files/pdf/storage_protocol_perf.pdf] shows that throughput drops on some FC arrays, though they didn't specify which ones... Check out <a href="http://blogs.vmware.com/performance/2008/02/scalable-storag.html" target="_blank">more performance suggestions on the VMware performance blog</a>!

    1. Align your virtual disk starting offset to your array. A simple way to do this is to boot the VM and use diskpart, assuming you're using Windows. Misaligned disk offsets can double disk I/O, or halve performance, depending on how you look at it...

    2. If you are using shared storage and want virtual disks greater than 256 GB, you must use a VMFS block size larger than 1 MB. Or you could just use raw device mapping or NFS!

    3. If using iSCSI or NFS, use a separate network or VLAN and consider an iSCSI HBA. These cut down CPU load significantly in high-I/O situations.

    4. De-duplication primary storage can have a huge impact on VMDKs created from a template! See if your array supports this!

    5. Thin provisioning can also be very useful in virtual machine storage, since a lot of VMDK space is empty...

Consider using NFS instead of FC/iSCSI with VMFS or RDM. It's pretty cool what modern NFS servers can do! See NetApp's Best Practices doc , for example.</li> </ol> VMware Storage Tidbits was originally posted at Stephen Foskett's Pack Rat blog on 22. Feb, 2008. Watch the Virtual Storage category for more
Version history
Revision #:
1 of 1
Last update:
‎06-05-2010 08:10 AM
Updated by: