VMware 5.0 ships with a new feature known as VM Storage DRS. Though you're probably more familiar with host DRS, don't confuse the two. Storage DRS' design is to take some pressure off of VMware administrators by providing some features that we, as VMware administrators (I'm one), have only dreamed about. Storage DRS (SDRS) performs the same magic as does host DRS (DRS) but with storage. SDRS automatically selects the best data store for your new VM and it constantly checks all possible data stores to balance I/O activity for best performance.
Notable VMware 5.0 DRS Features:
- Initial placement based on usage and I/O.
- Space load balancing.
- I/O load balancing.
- VM affinity and anti-affinity rules.
- VMDK affinity and anti-affinity rules.
- LUN maintenance mode.
Initial LUN placement will ease the burden of having to manually hunt for a LUN with enough disk space and I/O capacity to handle the new VM. The general practice is to find one with enough available space and plop it down without analyzing disk performance.
Space and I/O load balancing are important to maintain peak performance for VMs of all types. In any environment, you'll have VMs performing a variety of functions: web services, network services, database services, applications and more. It's almost impossible to keep track of how VMs interact on a LUN without excellent performance monitoring in place. And, out-of-the-box VMware 3.x and VMware 4.x just don't do it.
I like the idea of having affinity and anti-affinity rules for VMs and their corresponding disk images. Sometimes it's prudent to keep the VMDKs together on the same LUN but for performance reasons, there's no reason not to split them onto multiple LUNs. I often manually split up a VM's VMDKs for this reason. LUN mirroring for certain critical workloads is another feature of VMDK anti-affinity that I like.
Anti-affinity rules make sure that a VM's VMDK files are always on different LUNs.
Finally, LUN maintenance mode makes a lot of sense. We have a maintenance mode for hosts, so why not for storage? I don't like having to manually migrate VM disk files for storage maintenance. This feature makes the process automatic and pain-free.
SDRS first saw the public light of day at VMworld 2009 and it had many of us clamoring for the next major release. It's been a long time coming and we're glad it's finally here.
The only hitch with the whole converting to VMware 5.0's awesomeness is the awkward licensing. I think that this new license model will hinder adoption regardless of the length or depth of its feature list. Only time will tell but you're not likely to see large-scale VMware 5.0 deployments in live production environments for at least another two years.
Storage DRS might be one of the best features to arise out of VMware 5.0 but is it enough to make you switch? Talkback and let me know.