HP StoreVirtual VSA - SSDs and VMware

[RyanH]

The company where I work is planning on upgrading our servers to a new HP blade enclosure with 3 blade servers running ESXi. We are planning to run around 100 VMs from these. We would like to run the VMs off of SSD storage inside each server and use HP VSA to keep features like Vmotion and HA.

Has anyone used SSDs in a VSA before?

What sort of performance hit will it have compared to a physical LeftHand SAN?

Would a VSA bottleneck the speed of the SSD drives?

How much space is used up by having this configuration. I know with VMware's VSA RAID and the VSA use 75% of the available space. How does the StoreVirtual VSA compare?

[5y53ng]

The default for the volumes provided by the VSA is RAID-10, so your capacity on the virtual SAN is half of the physical capacity. In my experience the read performance of your disk system is the bottleneck. The RAID controller cache ensures the write latency is minimal. With SSDs I expect your read performance will be pretty good.

How SSDs do you have in each blade?

[oikjn]

CPU will be an issue.  You can now use two cores and that helps, but you want to get as quick of a core speed as possible as the CPU is critical and I have found that to be an issue when running VSAs at times.

[5y53ng]

Good point, I have seen CPU utilization at 100% during certain scenarios as well.

[RyanH]

Thanks for the feedback guys. We would be running 2 SSD's in  each blade. I think we are going to go with a physicial array. Its a shame HP doesn't have a cheaper SSD option than the P4900.

[oikjn]

If you have the time and already have the blade chassis and can swing one or two test blades for CPU/SSDs, the beauty of the VSA option is they actually let you test it 100% functioning for 60 days so you can spin up the VSAs, set them up and see how it works before spending anything on licensing.

There is no reason the SSD VSA's won't work.  I"ve done two cores on my hyper-v boxes without an issue, but my hardware is running at 2GHz and during snapshots or times of really heavy IO load it gets bogged down.  It doesn't slow down the other VMs on the systems, but I think 2GHz just isn't enough and if you can get something 3GHz it would really do well.  Anyway, if the company doesn't have the time to test or doesn't want to take the risk on spending an extra ~2k to test to see if you can save 20k, then I guess you are stuck with the physical.

[ryan_1212]

I am wondering, how would this play if you were to use an SSD accelerator card, like a fusion IO device or similar to cache hot blocks on the datastore which is hosting the VSA?  I have a feeling it might cause some wacky things to happen with sycronization and NR10 and end up not providing that large of a benefit.

[oikjn]

hot blocks are hot blocks so it really won't matter and adding an SSD accelorator card is a great way to speed up a VSA.  I've done it w/ LSI cards w/ cachecade2.0 and its great.  Only thing to keep in mind is if you do a lot of moving of luns or restriping/cluster migration type stuff, that will probably screw up what blocks are hot for a bit, but if you don't do things like that then an SSD card is definitely a great thing to add to a VSA.