[Samba] ceph_vms performance

[Jeremy Allison]

On Wed, May 23, 2018 at 02:13:30PM +0200, David Disseldorp via samba wrote:
> Hi Tom,
> 
> On Wed, 23 May 2018 09:15:15 +0200, Thomas Bennett via samba wrote:
> 
> > Hi,
> > 
> > I'm testing out ceph_vms vs a cephfs mount with a cifs export.
> 
> I take it you mean the Ceph VFS module (vfs_ceph)?
> 
> > I currently have 3 active ceph mds servers to maximise throughput  and
> > when I have configured a cephfs mount with a cifs export,  I'm getting
> > a reasonable benchmark results.
> 
> Keep in mind that increasing the number of active MDS servers doesn't
> necessarily mean that you'll see better performance, especially if the
> client workload is spread across the full filesystem tree, rather than
> isolated into the corresponding sharded MDS subdirectories.
> 
> > However, when I tried some benchmarking with the ceph_vms module, I
> > only got a 3rd of the comparable write throughput.
> > 
> > I'm just wondering if this is expected, or if there is an obvious
> > configuration setup that I'm missing.
> 
> My initial assumption would be that the improved CephFS kernel mount
> performance is mostly due to the Linux page cache, which is utilised
> for buffered client I/O.

Interesting. You might be able to improve the Samba vfs_ceph performance
by tuning the Samba write cache size (although for SMB2 leases this
isn't used).