[Gluster-users] Gluster speed sooo slow

[Brian Candler]

On Mon, Aug 13, 2012 at 09:40:49AM +0000, Fernando Frediani (Qube) wrote:
>    I think Gluster as it stands now and current level of development is
>    more for Multimedia and Archival files, not for small files nor for
>    running Virtual Machines. It requires still a fair amount of
>    development which hopefully RedHat will put in place.

I know a large ISP is using gluster successfully for Maildir storage - or at
least was a couple of years ago when I last spoke to them about it - which
means very large numbers of small files.

I think you need to be clear on the difference between throughput and
latency.

Any networked filesystem is going to have latency, and gluster maybe suffers
more than most because of the FUSE layer at the client.  This will show as
poor throughput if a single client is sequentially reading or writing lots
of small files, because it has to wait a round trip for each request.

However, if you have multiple clients accessing at the same time, you can
still have high total throughput.  This is because the "wasted" time between
requests from one client is used to service other clients.

If gluster were to do aggressive client-side caching then it might be able
to make responses appear faster to a single client, but this would be at the
risk of data loss (e.g.  responding that a file has been committed to disk,
when in fact it hasn't).  But this would make no difference to total
throughput with multiple clients, which depends on the available bandwidth
into the disk drives and across the network.

So it all depends on your overall usage pattern. Only make your judgement
based on a single-threaded benchmark if that's what your usage pattern is
really going to be like: i.e.  are you really going to have a single user
accessing the filesystem, and their application reads or writes one file
after the other rather than multiple files concurrently.

Regards,

Brian.