[Sheepdog] Sheepdog initial performance

[MORITA Kazutaka]

At Tue, 19 Jul 2011 11:30:57 +0200,
Benjamin Cleyet-Marrel wrote:
> 
> Hi,
> 
> We are currently in the process of evaluating sheepdog to use as a 
> backend storage for our virtual environement.
> But right now I am facing really  poor performances on unallocated bloc.
> It litterraly takes hours to  convert a 5G file.
> 
> So I am mounting the partition with different option without any luck
> /dev/sdd1 on /var/lib/sheepdog type ext4 
> (rw,noatime,user_xattr,barrier=0,data=writeback,nobh)
> Started sheepdog with
> sheep -p 7000 -l 0 /var/lib/sheepdog
> 
> When I issues
> qemu-img convert /images/debian60-64bits.qed -O raw sheepdog:debian60-64bits
> 
> It takes hours to finish altought it is just 5G img.
> The performance from within the virtual machine is then fine. and close 
> to raw performances.
> 
> Is there something I am doing wrong ?

Is the write cache enabled on your disk?  What is the result of
'hdparm -W /dev/sdd'?

Currently, Sheepdog works in a writethrough mode always, but other
formats work in a writeback mode when converting images.  So if the
write cache is not enabled on your disk, I think it causes a severe
difference.


Thanks,

Kazutaka