[Gluster-users] Question regarding write performance issues

[Ayelet Shemesh]

First - thanks for taking the time and providing the reply.

Due to a bad flu I was unable to verify till now but now saw we use fstream
in our apps, to write the files. Assumed the buffer was large, but never
tested it.

We have increased the fstream buffer to 100MB and will check if this helps
(this specific test can only be scheduled for later as the cluster is busy).

A related question:
I was wondering if there is any "magic number" as to number of files per
directory in Gluster volumes.
Some of my directories contain an order of 10^5 files and I'm begininng to
suspect this too (when I worked in local FS I didn't see a noticable
degradation, though).

Thanks again!
Ayelet

On Thu, Jan 17, 2013 at 5:28 PM, harry mangalam <harry.mangalam at uci.edu>wrote:

> Just a guess, but how are the writes being done?  If they're being written
> in
> zillions of tiny writes, then what you may be seeing is described here:
> <http://moo.nac.uci.edu/~hjm/bduc/BDUC_USER_HOWTO.html#writeperfongl>
> and the following stanza on named pipes.
>
> This is often the case with the large files being used in NGS/HTS where the
> fasta/fastq files are composed of millions of short (60-100 char) lines of
> characters and are typically written line-by-line.
>
> hjm
>
>
>
> On Wednesday, January 16, 2013 02:47:37 PM Ayelet Shemesh wrote:
> > Hi to all Gluster experts,
> >
> > I have a cluster of 10 machines exposing a volume into which 12 other
> > machines do many writes of large files (~100-300MB each).
> > In general I'm very happy with gluster. It's a great solution, and is
> quite
> > stable (thanks for the great work!).
> >
> > However, I have a problem which I was unable to solve yet, nor find any
> > solution to in the documentation or on this list archive.
> >
> > When the client machines write locally, and then just copy the files they
> > created to the gluster mount - everything works great.
> > When the client machines write directly to the gluster mounted volume I
> get
> > a huge performance hit.
> > In one specific test case the difference was 20 minutes for the copy and
> 8
> > hours for the direct write.
> >
> > I tried to set the iocache attributes of write-behind-window and
> > flush-behind, but to no avail.
> >
> > I will very much appreciate your help in solving this problem.
> >
> > Thanks,
> > Ayelet
>
>
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