[Gluster-users] [Linux-cachefs] [Gluster-devel] Can I use FSCache/Cachefiles with Gluster Native Client mode?

Suresh Jayaraman sjayaraman at suse.com
Thu Dec 6 09:17:58 UTC 2012

On 12/06/2012 12:24 AM, Anand Avati wrote:
> I believe FSCache must first be implemented in FUSE before any userspace
> filesystem (like GlusterFS) can make use of it?

Sounds about right to me.  Then, FUSE can ask FS-Cache to store / fetch
data on behalf of Glusterfs.

> On Wed, Dec 5, 2012 at 1:29 AM, 吴巍 <wuwei.tsh at gmail.com
> <mailto:wuwei.tsh at gmail.com>> wrote:
>     __
>     Now I'm sure that Gluster FS native client don't support FSCache.

But wait, why do you really need FS-Cache in your case? If improving
(re)-read performance is what matters to you, have you already taken a
look at the IO-Cache translator the Glusterfs provides?

Do you have a really slow network? Do you intend to keep your cache on
an SSD?
Note that FS-Cache/Cachefiles is not supposed to improve performance for
all kinds of workloads.

May be one way to know if your workload can benefit with FS-Cache or not is:
   - enable FS-Cache in NFS and try accessing the Gluster namespace via NFS
   - compare its performance with FS-Cache on NFS disabled

>     There are no codes about FSCache in the source code of Gluster FS.
>     the command  "mount -t glusterfs server1:/test-volume /mnt/glusterfs
>     -o fsc"  will be executed by /sbin/mount.glusterfs, and the "-o fsc"
>     option will be ignored silently.  
>     Thanks for everybody.
>     ------------------------------------------------------------------------
>     Wei Wu
>     *From:* Suresh Jayaraman <mailto:sjayaraman at suse.com>
>     *Date:* 2012-12-05 15 <tel:2012-12-05%C2%A015>:06
>     *To:* 吴巍 <mailto:wuwei.tsh at gmail.com>
>     *CC:* Ric Wheeler <mailto:ricwheeler at gmail.com>; gluster-users
>     <mailto:gluster-users at gluster.org>; linux-cachefs
>     <mailto:linux-cachefs at redhat.com>; gluster-devel
>     <mailto:gluster-devel at nongnu.org>
>     *Subject:* Re: [Linux-cachefs] [Gluster-devel] Can I use
>     FSCache/Cachefiles with Gluster Native Client mode?
>     On 12/03/2012 05:59 PM, Ric Wheeler wrote:
>     > On 12/02/2012 10:29 PM, 吴巍 wrote:
>     >> Hey,
>     >>
>     >> I Download the GlusterFS 3.2.7 Release and it works well. And I want
>     >> to improve the reading performance with FSCache/Cachefiles model.
>     >> I use the command line:
>     >> mount -t glusterfs server1:/test-volume /mnt/glusterfs -o fsc
>     >> and no error reported. But the local cache function of FSCache is not
>     Does Glusterfs support fscache? File systems typically have to be
>     modified to include support for fscache (see fs/cifs/fscache*.[c,h] or
>     fs/nfs/fscache*.[c,h] in the kernel source for example). IOW, they have
>     to be fscache aware to be able to use the persistent disk caching.
>     Have you checked if the option 'fsc' is being silently ignored? Try
>     mounting with '-vvv' to see whether it reveals more.
>     What do you mean by "local cache function of FSCache is not active"? Did
>     you mean that the files are not getting cached? or File are not being
>     fetched from the cache when re-read?
>     If it is already supported, are you running the cachefilesd user-space
>     daemon?
>     FS-Cache by default uses /var/cache/fscache dir for caching. You could
>     check whether the cached files are being seen there.
>     Also, /proc/fs/fscache/stats might reveal more details about pages
>     marked for caching, retrieved successfully from cache or cache returned
>      -ENODATA etc.
>     >> active. How can I use the local cache function of FSCache with Gluster
>     >> Native Client  mount mode?
>     >>
>     > Adding in the fscache list to see if anyone there has experimented with
>     > this,
>     > 

Suresh Jayaraman

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