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Re: [Xen-users] iscsi vs nfs for xen VMs

To: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Subject: Re: [Xen-users] iscsi vs nfs for xen VMs
From: Jia Rao <rickenrao@xxxxxxxxx>
Date: Mon, 10 Aug 2009 10:28:02 -0400
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dm-ioband seems to work with the new kernels (2.6.31). We are still using and reluctant to upgrade to a new kernel.
Can dm-ioband work with older kernels?


On Sun, Aug 9, 2009 at 11:11 PM, Fajar A. Nugraha <fajar@xxxxxxxxx> wrote:
On Fri, Aug 7, 2009 at 8:48 PM, Jia Rao<rickenrao@xxxxxxxxx> wrote:
> I prefer the second approach because I need tapdisk (each virtual disk is a
> process in host machines) to control the IO priority among VMs.

You can still control IO priority for block device using dm-ioband.

As for iscsi or nfs, the general rule would be that nfs is easier, but
you need a high-performance nfs server to get decent performance
(NetApp comes to mind).

If you've already tried nfs and not satisfied with its performance,
then you shoud try iscsi. Each domU storage exported as a block
device, imported on dom0 ,and use /dev/disk/by-path/* in domU config.
It should give simple-enough (e.g. no cluster fs required) setup,
decent performance, and it's still possible to control disk I/O
priority and bandwitdh.


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