It seems that a lot of vendors are starting to update their firmware to enable virtualized workloads from the vStorage APIs for Array Integration, also known as VAAI. Not only the vendors are starting to show interest, also the bloggers are picking up on it. Hence the reason I wanted to reiterate some of the excellent details out there and wanted to make sure everyone understands what VAAI brings. Although currently there are “only” three major improvements they can and probably will make a huge difference:
- Hardware Offloaded Copy
Up to 10x faster VM deployment, cloning, Storage vMotion etc. VAAI offloads the copy task to the array, enabling the usage of native storage based mechanism resulting in a decrease of deployment time but equally important reducing the amount of data flowing between the array and server. Check this post by Bob Plankers and this one by Matt Liebowitz which clearly demonstrates the power of hardware offloaded copies! (reducing cloning from 19Minutes to 6Minutes!)
- Write Same/Zero
10 x times less I/O for common tasks. Take for instance a zero-out process. It typically sends the same SCSI command several times. By enabling this option the same command will be repeated by the storage platform resulting in reduced utilization of the server while decreasing the time span of the action.
- Hardware Offloaded Locking
SCSI Reservation Conflicts…. How many times have I heard that during Health Checks / Design Reviews and while troubleshooting performance related issues. Well VAAI solves those issues as well by offloading the locking mechanism to the array, also known as Atomic Test & Set aka ATS. It will more than likely reduce latency in an environment where thin-provisioned disks are used or linked clones, or even where VMware based snapshots are used. ATS removes the need to lock the full VMFS volume but instead locks a block when an update needs to occur.
One thing I wanted to point out here, which I haven’t seen mentioned yet, is that VAAI will actually allow you to have larger VMFS volumes. Now don’t get me wrong, I am not saying that you can go beyond 2TB-512b by enabling VAAI… My point is that by having VAAI enabled you will reduce the “load” on the array and on the servers. I placed quotes around load as it will not reduce the load from a VM perspective. What I am trying to get at is that many people have limited the amount of VMs per VMFS volume because of “SCSI Reservation Conflicts”. With VAAI this will change. Now you can keep your calculations “simple” and base your VMFS size on the amount of eggs you can have in a single basket and the sum of all VMs IOPS requirements.
After reading about all of this goodness I bet many of you want to use it straight away, well of course your array will need to support it first. Tomi Hakala created a nice list of all storage platforms that are currently supported and those that will be supported soon including a time frame. If your array is supported this KB explains perfectly how to enable/disable it.
I started out with saying that there are currently only three major enhancements…. that means indeed that there is more coming up in the future. Some of which I can’t discuss and others that I can as those were already mentioned at VMworld. (If you have access to TA7121 watch it!) I can’t say when they will be available or in which release, but I think it is great to know more enhancements are being worked on.
- Dead Space Reclamation
Dead space is previously written blocks that are no longer used by the VM. Currently in order to reclaim diskspace (for instance when you’ve deleted a lot of files) these blocks you will need to zero them out with for instance sdelete and then Storage vMotion the VM. Dead Space Reclamation will enable the storage system to reclaim these dead blocks by giving block liveness information.
- Out-of-space conditions notifications
This is very much an improvement for day-to-day operations. It will enable notification of possible “out-of-space” conditions on both the array vendor’s tool both also within the vSphere client!
Chad Sakac – What does VAAI mean to you?
Bob Plankers – If you ever needed convincing about VAAI
AndreTheGiant – VAAI
VMware KB – VAAI FAQ
VMware Support Blog – VAAI changes the way storage is handled
Matt Liebowitz – Exploring the performance benefits of VAAI
Bas Raayman – What is VAAI, and how does it add spice to my life as a VMware admin?