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…

1. Beware of block sizes greater than 256 KB when using certain Fibre Channel arrays!  VMware’s performance research shows that throughput drops on some FC arrays, though they didn’t specify which ones…  Check out more performance suggestions on the VMware performance blog!
2. 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…
3. 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!
4. 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.
5. De-duplication primary storage can have a huge impact on VMDKs created from a template!  See if your array supports this!
6. Thin provisioning can also be very useful in virtual machine storage, since a lot of VMDK space is empty…
7. 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.

If you’ll be in Washington DC on March 4, or Durham NC on March 6 and are interested in the world of storage and server virtualization, I’d love for you to register and attend this free seminar!