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Virtual Machines on Drobo S


todarsey
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I have recently purchased a Drobo S for use with Windows Server 2008 R2 Hyper-V. Well one thing I have noticed is a dramatic decrease in speed in my VM performance compared to when the VM's were connected via sata. I was assuming that connecting the Drobo S via esata would have been good enough but I guess I assumed wrong. The esata is integrated into the mother board and the motherboard is an Asus M4A78T-E and here are the rest of the specs.

AMD Athlon II X2 3.0GHz processor

8GB RAM

Drobo S - 5TB

I have ACHI driver installed.

Is there something I need to look at changing in the BIOS or something else I need to try? Or, am I just SOL?

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In looking at the reviews for the thing, it's really only capable of sustaining reads and writes at around 70MB/sec, which is about 1/2 as fast as a non-RAID setup on the average internal SATAII drives in most machines (usually a little above 130 - 140MB/sec even on cheaper controllers), and an internal SATAII RAID controller (like the ICH10R) yields on average 200 - 350MB/sec (or higher, depending on the drives - mine are simple WD 7200RPM drives and I get just over 360MB/sec sustained to a RAID10).

You'd have been better off with an iSCSI enclosure, honestly, if you wanted speed.

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So do you think a Drobo FS or a Drobo Pro work better for my needs since they have iSCSI? I am assuming that the Drobo FS uses iSCSI since it uses an ethernet port but it doesn't say iSCSI in any documents I have seen. I know the Drobo Pro does.

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No, I'm saying that an external enclosure isn't going to gain you any speed (the iSCSI is potentially as fast as a single internal disk, but depending on the NICs at each end may end up only being as fast as the Drobo S). I'm saying if you want speed similar to that of an internal disk, you'll have to pay good money for it from an external enclosure (thousands of dollars at least, not a few hundred). Those enclosures you're using and/or thinking of using aren't meant for regular use, they're designed for storage. Speed is not one of their main goals.

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I have recently purchased a Drobo S for use with Windows Server 2008 R2 Hyper-V. Well one thing I have noticed is a dramatic decrease in speed in my VM performance compared to when the VM's were connected via sata. I was assuming that connecting the Drobo S via esata would have been good enough but I guess I assumed wrong. The esata is integrated into the mother board and the motherboard is an Asus M4A78T-E and here are the rest of the specs.

cluberti has already touched on many of the points on why you wouldn't do this on a lower-end enclosure like this. The only thing I want to do is explain why you're seeing the dropped performance. :)

When you had the VMs on the internal storage each drive had it's own SATA connection for communicating with the host controller. This meant that reads or writes happening to multiple drives at the same time had dedicated channels for each drive. When you moved to the Drobo S the configuration changed so that all of the drives are funneled through a single connection to the host controller. You drastically reduced the overall bandwidth available to the drive subsystem by doing this.

Moving to the Drobo FS or even Drobo Pro isn't really doing to solve this problem. The Drobo Elite may be a slightly better solution since it has dual iSCSI connections, but I don't think it'll be as good as your internal drive solution was.

Is this for a single server or are you trying to move to a clustered Hyper-V solution? For a single server there's really no good reason, other than adding spindles, to move to external storage. Adding more spindles doesn't do much good if you don't have the proper connection between the server and the storage because you can't take advantage of the additional throughput. And, as you found out, the wrong connection type can actually make performance worse.

Edited by nmX.Memnoch
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