Re: [Xen-users] LVM over FC-San poor performance

[Jan-Aage FrydenbÃ-Bruvoll <jan@xxxxxxxxxxxxx>]

Hi,

On Tue, Apr 19, 2011 at 09:26, Mice <mice1982@xxxxxxxxx> wrote:
>
> Hi, all
>
> We are about to test the performance with FC-SAN
> Currently there are 15 Hypervisors connected to a 16T LUN with 4G fiber 
> channel.
> LVM is used to manage the VM's disks, VM's disk image is created as logic 
> volume over the LUN.
> All VMs are HVM.
>
> when dd the lv from dom0, the performance is acceptable, range from 150 ~ 
> 300MB/s
> but when dd the local disk in guestOS (centOS 5.5 domU), the peformance is 
> poor, about 40MB/s
>
> my question is, is this normal? if not, any clues for performance tuning?

For what it's worth, I am struggling with a structurally similar
problem, although the underlying infrastructure is different. I have a
Nexenta storage server with COMSTAR iscsi set up - the performance is
acceptable from the dom0s (the network infrastructure becomes the
limiting factor before the server starts struggling), but as soon as I
benchmark the (paravirtualised) VM disks, I get similar numbers to
what you outline in your posting.

I am quite keen to find the source and a solution to this - if there
is anything I can contribute with along the way, please let me know.

Best regards
Jan

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