is fast a fit for general virtualization workloads?

Hi all,

Test setup

2 x esxi 4.1 hosts

cx4120

5x100gb efd/5x300gb fc/ 5x1tb sata - all in a storage pool with auto tiering enabled

2x100gb efd for fast cache

I have been doing some testing and reading on Fast. I see the benefits immediately.. hit a server with high io and sure enough blocks of data are moved up to flash drives and the io throughput increases from say 3000 io/s to 9000 with an 8kb block (50/50 read/write 50/50 random sequential) – and latency drops from 30ms to 2.9ms – all superb.

I do have some concerns though.

First, we will be backing up the infrastructure every night (exact solution still to be decided) that is a heck of a lot of i/o – I would think that the biggest servers (.vmdk files) would be generating the most i/o simply due to the size of them and the amount of time taken to transfer them to whatever medium we use for backups. Hence even if a server is very low in i/o requirement during the day if it has a large disk it will be moved up the tier due to the IO generated during the backup cycle, so we could have a small database that has a high i/o requirement that gets moved down the tier due to a big disk on a very underutilised server.

So I read a bit and found this. http://www.emc.com/collateral/hardware/white-papers/h8057-fast-sap-unified-storage-wp.pdf

And got all warm about fast again until I found this:- page 18

 

It’s the last last line that has me worried.. “totally different types of work” “during the day and night” – just what I had been thinking – we have a stupidly different environment, 100 vm’s with lots of different apps/databases etc. – then we will be generating lots of traffic at night backing it all up.

I suppose if you could configure fast with a time window when NOT to collect data results that would nail the day and night problemit.. but I can’t see that option.

I still don’t like the statement about “totally different types of work though”

The conclusion doesn’t read any better.

So the question is.. fast or no fast?

GFord@a4e.co.uk