[sheepdog-users] Concern about sheepdog performance

[Liu Yuan]

On 12/18/2012 06:07 PM, Valerio Pachera wrote:
> I updated my sheepdog to latest develop version (0.5.5_19_g395c05c).
> 3 nodes, copies 2.
> I also tried to add allocsize=4M because I know sheepdog uses file of 4M.
> Is it a good idea?

No effect. how big the request size is decided by the kernel.But you can
actually increase the performance a bit by tuning block layer's queue
parameter.

Most of kernel inside VM will never successfully issue the request as
big as 4M  to the block device(For us, it is Sheepdog). For Linux
kernel, the possible method is use 'virtio' and change
'/sys/block/vda/queue/max_sectors_kb' as 4096k. This will improve the
throughput a bit, but not as optimal in theory. (I have tested RHEL 6's
kernel, it won't issue 4M request as set) I am not sure current upstream
Linux kernel will do the job as expected.

Thanks,
Yuan