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faster storage for virtual machines

K

kick

Limp Gawd
Joined
Jul 24, 2005
Messages
210
Dealing with some I/O contention with my Win7 virtual machines, which are stored on a single disk... read/write/response time/queue length are all horrible. I'm considering an eSATA solution so I can spread the VMs across multiple disks, something like the Sans Digital TowerRAID+:

http://www.sansdigital.com/towerraid-/tr4mplusb.html
http://www.sansdigital.com/towerraid-/tr5mplusb.html

Both are bundled with the 2-port HighPoint RocketRAID 622 (http://www.highpoint-tech.com/USA_new/cs-series_rr600.htm). It features port multiplication, but seems like a fairly basic controller otherwise.

I'm curious to hear any input on how this setup is likely to perform and if the controller will be up to the task. It doesn't need to be blazing fast, just not fall to it's knees when I'm taking an image of one VM and continuing with development work on a couple others.

Thanks!
 
How many VM's are you running concurrently and what OS's and major apps are you running inside them? Is the machine config the one in your sig (If it is, the first thing I will suggest is to max out your RAM and upgrade the base OS to Win7 from Vista) and what kind of disk are they currently on?
 
It's my work machine -- Dell OptiPlex w/ i5-2500 and 8GB running Win7. VMs are on a single secondary drive, which isn't exactly 'speedy' (Seagate 500GB 7200.9).

VMs are mostly Win7 used for app testing/integration work and development of corporate software images. Ideally, I'd like to be able to have one/two VMs creating/restoring images while using one/two VMs for dev work, all without disk performance becoming abysmal. That's why I'm looking to an eSATA enclosure with 4-5 individual drives. Basically, one VM per drive to hopefully avoid contention.
 
Why not SSD? Thats going to beat disks for this kind of stuff except for pure storage capacity.
 
I'm not familiar with that hardware, but with Silicon image controllers and multipliers, performance is divided by the number of drives. It's clearly not performance oriented.
 
SSDs: cost. I'd likely not get approval for the purchase unless it's the only course of action...

Aesma: Any numbers re: divided performance? It doesn't sound good, but potentially acceptable if the end result still beats the <10MB reads and triple digit response times I'm currently seeing.

I checked with the vendor (Sans Digital) and they suggested mini-SAS over eSATA. The enclosure/controller are a little more, but not crazy.
 
kick said:
SSDs: cost. I'd likely not get approval for the purchase unless it's the only course of action...

Aesma: Any numbers re: divided performance? It doesn't sound good, but potentially acceptable if the end result still beats the <10MB reads and triple digit response times I'm currently seeing.

I checked with the vendor (Sans Digital) and they suggested mini-SAS over eSATA. The enclosure/controller are a little more, but not crazy.
Click to expand...

How much capacity do you need? The Sans Digital enclosure is $300 by itself, then count the 4-5 drives and controller. In just pure IO a single SSD is going to beat all 5 spinning disks for running VMs.
 
kick said:
SSDs: cost. I'd likely not get approval for the purchase unless it's the only course of action...

Aesma: Any numbers re: divided performance? It doesn't sound good, but potentially acceptable if the end result still beats the <10MB reads and triple digit response times I'm currently seeing.

I checked with the vendor (Sans Digital) and they suggested mini-SAS over eSATA. The enclosure/controller are a little more, but not crazy.
Click to expand...

How much space do you actually need for the VM's you are using? The eSata solutions you are looking at are port multiplier based and will still be limited performance-wise. You would be much better served by using internal drives in R0/10 or a HW RAID6 array for the additional speed (4 external drives on a single eSata to SATA2 port multiplier share a single 300MB connection (Regardless of scheme) to the computer where 4 drives hooked to a HW RAID card have almost 1200MB of bandwidth. A lot depends on how large your VM's are, how many you are running concurrently and what kinds of applications you actually run to the best connection method. SSD prices have dropped so low recently they in some way would likely benefit you in some way in this plan.
 
I really appreciate all the comments -- been away from the [H] forums for too long!

Ideally, 1TB should give enough working space.

SSDs present a cost issue -- 4 x ~250GB or 2 x ~500GB drives would run close to $700 or more depending on brand/model (Canadian pricing) and I'd still need an enclosure as my Dell minitower only accommodates two internal drives. I also work for a publicly funded institution, so dollars are limited.

From comments here and reading various resources, I see the shortfalls of the eSATA/port multiplier approach... does the same go for mini-SAS? The eSATA solution ($150) came with a PCIe x1 controller but the mini-SAS version ($350) comes with a PCIe x4 card and I understand mini-SAS actually affords four lanes per connector (one drive per lane) vs simply dividing the single lane across multiple drives. Still not sufficient?
 
Yep, they're funky toolless bays with sleds tho. I tried putting a spare 60GB Vertex 3 into one yesterday and the pins in the sled only line up with the rear mounting holes on the OCZ bracket. I could look for another adapter, but that would mean using one of the SSDs for both boot and VM storage... not a problem?
 
You could also velcro tape the ssd to the case. We had a few machines here we did that with. No issues so far (12 mos+).
 
I'd look into some Samsung 830 series SSDs and see if you can offload the large storage to a 1-2tb fast drive. That'd keep your costs low and still give you the performance you need.
 
For mini-SAS you'd need a HBA.

With a SATA port multiplier, if you have 100MB/s drives and use two concurrently you'll get 50MB/s each, 4 => 25MB/s. I use mine only for storage so it's possible with high I/O it would be much worse.
 
kick said:
Yep, they're funky toolless bays with sleds tho. I tried putting a spare 60GB Vertex 3 into one yesterday and the pins in the sled only line up with the rear mounting holes on the OCZ bracket. I could look for another adapter, but that would mean using one of the SSDs for both boot and VM storage... not a problem?
Click to expand...

There are a lot of "two 2.5 inch to 3.5 inch" adapters. Just buy one with a standard hole pattern.

Using the ssds as a boot drive isn't going to be an issue unless you'll be running VM's with extraordinary I/O requirements.
 
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