Re: Why does btrfs benchmark so badly in this case?

[Josef Bacik <jbacik@fusionio.com>]

On Fri, Aug 09, 2013 at 11:35:33PM +0200, Kai Krakow wrote:
> Josef Bacik <jbacik@fusionio.com> schrieb:
> 
> >> So I guess the reason that ZFS does well with that workload is that
> >> ZFS is using smaller blocks, maybe just 512B ?
> > 
> > Yeah I'm not sure what ZFS does, but if you are writing over a block and
> > the size/offset isn't aligned then you'd see similar issues with ZFS since
> > it would
> > have to read+modify+write.  It is likely that ZFS just is using a smaller
> > blocksize.
> 
> From what I remember, ZFS uses dynamic block sizes. However, block size can 
> be forced and thus tuned for workloads that require it:
> 
> http://www.joyent.com/blog/bruning-questions-zfs-record-size
> 
> Maybe that's the reason...
> 
> It would be interesting to see how the benchmarks performed with forced 
> block size.
> 

When I did bs=4k in the fio job to force it to use 4k blocksizes we performed
the same as ext4 and xfs.  Thanks,

Josef