Friday, September 07, 2007

VMware over NFS

My background is Fibre Channel and since 2003 I've followed iSCSI very closely. In fact, for years I have never paid much attention to other protocols until recently. For a long time I felt that FC was good for everything, which sounds weird if you consider who my employer is but then again, NetApp didn't hire me for my CIFS or NFS prowess. I was hired to drive adoption of NetApp's Fibre Channel and iSCSI offerings as well as the help prospects realize the virtues of a Unified Storage Architecture.
And speaking of Unified architectures leads me to VMware which represents to servers exactly what NetApp represents to storage. A Unified architecture with choices, flexibility, and centralized management without shoving a specific protocol down someones throat.
Close to 90% of the VI3 environments today are deployed over FC and of that %, based on experience, I'd say that 90% are using VMFS, VMware's clustered filesystem.
If you are dealing 2-3 clustered ESX, these types of deployments are not very complex. However, the complexity starts to increase exponentially as the number of servers in a VMware Datacenter start to multiply. RAID Groups, LUNs, LUN IDs, Zones, Zone management, HBAs, queue depths, VMFS Datastores, RDMs, multipathing settings etc.
Then the question comes up...VMFS LUNs or RDMs. How's my performance is going to be with 8-10 VMs on a VMFS LUN and a single Disk I/O queue? What if I take the RDM route and later one i run out of LUNs?
Way to many touch points, way too many things to pay attention to, way to many questions.
Well, there's help...NFS. I've recently had to the opportunity to play with NFS in my environment over VMware, and I can tell you, you are missing out if you at least do not consider it and test it for your environment.
Here's what I have found out with NFS and I'm not the only one:
  • Provisioning is a breeze
  • You get the advantage of VMDK thin Provisioning since it's the default setting over NFS
  • You can expand/decrease the NFS volume on the fly and realize the effect of the operation on the ESX server with the click of the datastore "refresh" button.
  • You don't have to deal with VMFS or RDMs so you have no dilemma here
  • No single disk I/O queue, so your performance is strictly dependent upon the size of the pipe and the disk array.
  • You don't have to deal with FC switches, zones, HBAs, and identical LUN IDs across ESX servers
  • You can restore (at least with NetApp you can), multiple VMs, individual VMs, or files within VMs.
  • You can instantaneously clone (NetApp Flexclone), a single VM, or multiple VMs
  • You can also backup whole VMs, or files within VMs

People may find this hard to believe, but the performance over NFS is actually better than FC or iSCSI not only in terms of throughtput but also in terms of latency. How can this be people ask? FC is 4Gb and Ethernet is 1Gb. I would say that this is a rather simplistic approach to performance. What folks don't realize is that:

  • ESX server I/O is small block and extremely random which means that bandwidth matters little. IOs and response time matter a lot.
  • You are not dealing with VMFS and a single managed disk I/O queue.
  • You can have a Single mount point across multiple IP addesses
  • You can use link aggregation IEEE 802.3ad (NetApp multimode VIF with IP aliases)

Given that server virtualization has incredible ramifications on storage in terms of storage capacity requirements, storage utilization and thus storage costs, I believe that the time where folks will warm up to NFS is closer than we think. With NFS you are thin provisioning by default and the VMDKs are thin as well. Plus any modification on the size of the NFS volume in terms of capacity is easily and immediately realized on the host side. Additionally, if you consider the fact that on average a VMFS volume is around 70-80% utilized (actually that maybe high) and the VMKD is around 70% you can easily conclude that your storage utilization is anywhere around from 49-56% excluding RAID overhead, then NFS starts to make a LOT of sense.

VMworld is next week and NetApp is a platinum sponsor. So, if you are attending, I would recommend you drop by Booth 701 and take a look at some incredibly exciting demos that have been put together showcasing the latest NetApp innovations with ESX server as well as VDI.

I'm hoping to be uploading the demo videos here next week or have links to them .