As I blogged previously, VAAI support for XIV has two dependencies:
- 10.2.4a code
- Vmware Certified driver
Both of these things are very close to release….
In the meantime I have had the chance to demonstrate the uncertified VAAI driver with XIV 10.2.4 code, just to see what affect it has.
And what is the affect?
VAAI dramatically reduces the amount of work that the vSphere 4.1 server needs to do to get things done.
The XIV implementation of VAAI provides the three fundamentals of VAAI:
- Full clone, copying data from one logical unit (LUN based) to another without writing to the ESX server.
- Block Zeroing, assigning zeros to large storage areas without actually sending the zeros to the storage system.
- Hardware Assisted locking, locking a particular range of blocks in a shared logical unit (providing exclusive access to these blocks), instead of using SCSI reservation that locks the entire logical unit.
To test VAAI with XIV, I did two things: a VMDK migration (a Storage Vmotion) and VMDK cloning. I used the vSphere client to time how long the operation took and XIV Top to see how much IO was being generated by the vSphere server. Now please understand, these numbers and timings are based on a lab environment. The speed and peaks will vary from client to client and install to install.
Firstly the migration: I performed a migration of a VMDK from one data store to another. The migration without VAAI took 42 seconds as can be seen from the screen capture below:
The migration generated a peak of 135 MBps of traffic being written to the target volume as can be seen from XIV Top:
I then turned on VAAI and did the same migration. I won’t document the process to install the VAAI driver, as it will be different when the certified version is released. However after the driver is installed, I could turn VAAI on and off by toggling these settings from 0 1 and back again:
I we did another VMDK migration with VAAI enabled. This time the migration took 19 seconds (as opposed to 42 seconds), so an immediate improvement occurred.
When I checked XIV Top, there was no IO at all! In other words the vMotion was done with no apparent load on the vSphere HBAs or the SAN. I feel silly showing this screen capture, but this is what I saw…. nothing.
I then did a VMDK clone. The Data store was on XIV, VAAI was not enabled. There was no other IO running on the ESX server. The clone took 40 seconds (as reported by vCenter):
The clone generated a peak of 2 MBps for around 20 seconds (as reported by XIV Top). Almost no fibre channel IO was thus generated by the clone.
As I have blogged before, I will be repeating this whole exercise once I have real live customers running this configuration, so expect further updates.