[Gluster-devel] Caching support in glusterfs

[Niels de Vos]

On Tue, Nov 24, 2015 at 10:35:20AM -0500, Jeff Darcy wrote:
> 
> 
> 
> On November 24, 2015 at 6:47:59 AM, Avik Sil (avik.sil at hgst.com) wrote:
> > While searching for caching support in glusterfs I stumbled upon this
> > link:
> > http://www.gluster.org/community/documentation/index.php/Features/caching  
> >  
> > But I didn't get much info from it. What is plan ahead?
> 
> There is some ongoing work on creating and improving the support
> necessary to support caching/delegations in Ganesha (NFS) and Samba
> (SMB).  Perhaps members of those teams could elaborate.  Unfortunately,
> there’s no current work on using those same features to create a
> generalized caching layer within “core” (native protocol) GlusterFS
> itself.  While there’s broad agreement that it would be useful, such an
> effort requires someone to lead/drive it and nobody has stepped up to do
> so.

Both the Linux NFS client (nfs kernel module) and the Linux SMB client
(cifs kernel module) support client-side read-caching through FS-Cache.
To use this, you basically do the following:

  # yum install cachefilesd
  # systemctl enable cachefilesd
  # systemctl start cachefilesd

  # mount -t nfs -o fsc storage.example.com:/volume /mnt

The above is from memory, and may not be completely correct. You can
find more details here:

  http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/caching/fscache.txt
  http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/caching/cachefiles.txt

There was a start to add support for FS-Cache to the FUSE kernel module,
but progress on that has stalled for a while. Assistance with that is
welcome, and I can find the work-in-progress patches if someone is
interested in helping out.

HTH,
Niels
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