Re: [Xen-users] Xen SAN Questions

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

On Wed, Jan 28, 2009 at 9:09 PM, Tait Clarridge
<Tait.Clarridge@xxxxxxxxxxxx> wrote:
> Well I figured out one thing, that my numbers were totally off for EXT3 and 
> XFS without DRBD haha.
>
> I will do some more testing, I can't believe I ruled out "dd" as a viable 
> benchmark.
>
> *smacks forehead*
>
> Thanks for the help, I am testing with those DRBD config options now.

I'd be interested to hear about your results.

To tell the truth, I was tempted to try a similar setup. I decided
against it though, because :
- using local disks provide higher I/O throughput. Using
network-attach disks, however, is mostly limited by the network
interconnect speed. For example, 1 Gbps network link could only give
max (theoretical) throughput of 125 MBps while local disks can easily
give 235 MBps (tested with dd)
- active-active DRBD setup can produce split-brain

So in the end I settled for scheduled zfs-based backup. That is :
- when using opensolaris dom0, I can use zvol-backed storage and do
backups from dom0
- when using Linux dom0, I use zfs-fuse on domU and perform backups there.

Again, I'd be interested to hear about your results. If you can get
something like 200 MBps then I'd probably try to implement a similar
setup.

Hint : You probably want to stay away from GFS as domU's backend
storage. Just use LVM-backed storage (with cLVM, of course) for MUCH
faster performance. To measure its performance, a simple way is using
dd on the block device.

Regards,

Fajar

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