I was just handed a full shelf (15) of unused 5400rpm 300GB SATA drives. As of today, we've got 11 ESX hosts pointed at various 10k and 15k SCSI LUN's on this same SAN.
Keeping in mind that this shelf is going to be for "2nd tier" general-purpose VM's with little disk activity, how would you guys carve-up this shelf? How many RAID 5 arrays? Just one? How many hosts would you zone per LUN? Would you stick with 500GB LUN's, which seems to be the most often recommended size for general purpose VM's?
Our hosts range from 24GB to 48GB RAM and average 12-15 VM's per host.
Interested in the board's collective $.02!
Your performance is going to suffer, because 5400 RPM, but it could be useful.
You can try setting up RAID 5 (1) and test it, but SATA is good for long time archives, not really for VM's. But everyone has different type of environments, so you can always see for yourself. The more drives the better, so allocate the entire shelf as one big storage array.
With larger drives obviously your performance in RAID is going to decrease a little bit. I would say stick with your gut about what size to make the LUNs, if you aren't going to have any large vmdk files then 500GB should be fine. Slow storage arrays are nice for housing R&D VMs along with ISO's and anything else you just want to store. Not to mention you could replace those drives down the road if you wanted with faster ones for pretty cheap.
Good luck with the new storage
RParker is right about allocating the entire shelf as one big storage array. Then you can chunck it in multiple LUNs as you wish. I've already run, and still running, a few dev servers (web, developement, tests) and even domain controllers on SATA with no issue at all. As long as they are not trying to hammer the array all a the same time, it will be fine. Just ask / tell the users they will not have high disk IO... Sometimes, space is more important than speed - it just have to be secure and stable.
Thanks for everyone's help. We divided the shelf into two RAID-5 arrays with seven drives each. Each array is cut in half which yields two ~850GB LUN's per array. Yes, those LUN's are on the large side but again, this is for our do-nothing VM's that generate very little disk I/O. I'm not too worried about contention.
So far I have 18VM's running on one of the LUN's spread across four ESX hosts. They're doing just fine. They're plenty responsive. The moral of the story is not to fear 5400rpm SATA. It's useful, and the price (FREE in my case) is hard to beat.
we've 2 DAE of 15 sata disks of 500 GB 7200 in a cx700 storage. It's very hard to use a right use for these kind of disks.
For oltp and file server, the best raid configuration is RAID 3 instead of RAID 5. With RAID 5, I had fulfill all the write cache of my storage.
In vmware enviroment, we use it only for temporary storage for vcb export of vm. Nothing else!