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Re: [Xen-users] Shared Storage

To: Jonathan Tripathy <jonnyt@xxxxxxxxxxx>
Subject: Re: [Xen-users] Shared Storage
From: John Madden <jmadden@xxxxxxxxxxx>
Date: Mon, 25 Apr 2011 13:34:49 -0400
Cc: "xen-users@xxxxxxxxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxxxxxxxx>, Bart Coninckx <bart.coninckx@xxxxxxxxxx>, Jonathan Dye <jdye@xxxxxxxxxxxxxxxxxxxxx>
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I would honestly prefer to manage hundred of LVs instead of hundreds of
LUNs. I'm just concerned about the iSCSI bottleneck (if any) if I were
to create an LVM VG using a single iSCSI LUN for about 50 - 100 LVs. Any
advice is appreciated.

I'd be more concerned over iSCSI itself being able to scale based on your workload, especially if you're doing it over GbE. Even 50 VMs doing relatively little though concurrently could cause problems given the nature of iSCSI (TCP overhead, latency of ethernet, etc). My feel for this is that the fewer-LUN-more-LV route would be more efficient because you'll have fewer block device queues and multipath call-outs and such but that's just a guess on my part. Test it out, see which one is better. If there's no difference, go with the one that's easier to manage.


John Madden
Sr UNIX Systems Engineer / Office of Technology
Ivy Tech Community College of Indiana

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