[sheepdog-users] Issues with gateway mode

[Hitoshi Mitake]

Hi Gerald,

On Sat, Nov 7, 2015 at 9:05 PM, Gerald Richter <richter at ecos.de> wrote:
> Hi,
>
> I need to setup a storage cluster over slow network connections.
>
> Sheepdog in gateway mode seems to be the ideal solution for me. That mean I
> have three or more storage nodes and a lot of gateway node that only uses
> the sheepdog cache. As long as most request are statisfied by the cache
> (which is an ssd), performance should be ok. Slow network connection aren't
> a problem as long as the cache uses write back mode.
>
> I have setup a test environment with 0.9.2 . As long as the vm are small
> enough to fit completly in the cache it seems to work, but when the vm is
> bigger than the cache I get I/O errors after some time. Also after a reboot
> of the host machine it seems to take very long time, until I can boot the
> vm, also the cache is still uptodate.
>
> Browseing through the mailing list archive I found
> http://lists.wpkg.org/pipermail/sheepdog-users/2015-August/015120.html,
> where Hitoshi said "object cache is not maintained currently. Please do not
> use it.". Is this still true? or is there any way to use the setup I
> described above?

Yes, it's true. Please don't use object cache.

BTW, many gateways + fewer storage nodes is dangerous. Because the
gateways doesn't contribute to increasing parallelism of disk I/O. If
a number of VMs and storage nodes are unbalanced, performance of
virtual disks will be very bad. Could you provide a detailed number of
VMs, gateway nodes, and storage nodes?

Thanks,
Hitoshi

>
> Thanks & Regards
>
> Gerald
>
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