Decent hard drive setup for VMs

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Just wondering what the best setups for performance in VMware, in terms of storage.

Currently in my lab, my VMs are sat on a (4x1TB 7200rpm) RAID-5, which is being used for several other things as well, so I dont think the performance is that great.


I have room for 4 more drives in my RAID card, so I was considering buying a couple of drives (have to be 2.5") and set these up on a RAID-1, but obviously as they are 2.5", most are 5400rpm, some are 7200 (at a cost). I know revolutions isnt the be-all and end-all of disk performance, but I wondered if having a RAID-1 would give better performance? These would be in a storage pool / virtual disk separate to any other pools I have setup, so that should improve performance in itself?

Also considering the seagate momentus XT (hybrid SSD) drives, probably looking at approx £100 each for 500gb so would be £200 there, comparatively similar size 7200 regular HDDs are about 80-90 each anyway. Do you think I would get a decent performance increase with the "near SSD performance" of these hybrids? Or just stick with cheaper 5400 disks?

Open to ideas

 

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You're probably wasting your time with the hybrid drives in this instance, it uses the SSD part of the drive to cache the commonly used files but in the case of VM's these files are going to be large (VMDK's remember, you aren't storing the VM's individual files on your storage platform, you're storing the entire disk image).

As far as disk performance goes, you have a trade off here, you can go for striped disks where they are obviously going to be faster but... and this is important, if you lose a disk you lose the entire stripe set (unless of course you go raid 0+1 which gives you a mirrored stripe set but that again will have a performance hit because it's writing the data twice). This is the trade off with raid 5 where you can lose a single disk or raid 6 where you can lose 2 disks.

You need to decide whether you want performance or resiliance. Of course if you have an different location where you're backing up your VM's to (with something like Veeam or VDR) then you're going to be better off than if you don't have any backup at all and can run the risk of running a stripe set in your environment.

One word of advice with regards to the 2.5 drives, you will want to make sure you have plenty of cooling with those disks because running them in a raid set will increase the heat on them when compared to normal PC\Laptop use.

 

Thankas for the input simon.

Good point about the hybrids not having enough SSD space to be worthwhile, hadn't thought about that. They still seem like good value for money v performance, with the current prices!

I was probably going to go for a RAID-1, as I would like the redundancy, performance isn't critical as it works OK as it is now, I just think with how it is currently set up, especially with the parity aspect of the RAID-5, I think it is definitely a bottleneck in my setup. It is only a home lab but I would still like decent performance! It seems to struggle more when I have lots of VMs on the go (got about 10 currently) and I don't think it is down to the servers (they are using about 3% CPU) but I dont really know how to use vsphere well enough yet to look at the performance graphs etc, I might check later to see if I can make some sense of it. Might also check for queue length against the disks themselves on my RAID disks.

Currently, as I mentioned earlier, there is a RAID-5 setup - this is split into 2 pools, and one of these pools is then split into 2 partitions on one volume. On one of the partitions I use it as a storage are for all my general junk, software etc, it also is where my downloads are saved to and I am constantly downloading. On the other partition, I just have two StarWind iscsi IMG files which are my are my LUNs.
My idea was to create a separate storage pool on two new disks just dedicated to these IMG files for my vmware to use, so would I be correct in thinking that alone would improve the current performance?

Regarding the use of 2.5 disks, I have an enclosure which they will sit in which has 2 fans in the back to keep them cool, hopefully that should be enough to keep them happy

 

Go have a look at some of the performance figures I have over on my site, I tested a couple of different NAS\SAN devices\servers and tested a number of different configurations. A lot of the time the configuration is actually helped out if you have more ram.

What is it you're using as a NAS\SAN? FreeNAS or OpenFiler? Having tested both of those and having the performance metrics on my site you will be able to see which offers the better performance (I also tested NFS and iSCSI just to see what was on offer).

 

Thanks Simon,

Will take a look on your site. I use StarWind iscsi software, works really well - I tried OpenFiler but couldn't get on with it really! I'm happy with this as a SAN setup, but would try a different one if it would give better performance, I just think it is my disk setup which is the issue in this case... I have 4gb RAM in the PC which is hosting all these disks, it is server 2003 x86 and there isnt much else on there really so it should have plenty of RAM to play with!