[Gluster-devel] performance question

[Krishna Srinivas]

Hi Gerry,

Good observation. I was checking on the performance with
self-heal turned off and the turning it on.

On glusterfs mounted directory:
With self-heal on:
bash-3.1# time cp -r /etc/ .

real    0m28.048s
user    0m0.004s
sys     0m0.060s
bash-3.1# time rm -rf etc/

real    0m28.666s
user    0m0.000s
sys     0m0.032s
bash-3.1#

With self-heal off:
bash-3.1# time cp -r /etc/ .

real    0m2.376s
user    0m0.012s
sys     0m0.060s
bash-3.1# time rm -rf etc/

real    0m3.639s
user    0m0.000s
sys     0m0.000s
bash-3.1#

So there is significant difference. The difference is that there is no
external attributes management when the self-heal is off. AFR code
does getxattr/setxattr when self-heal is on, so this introduces
some overhead. Also there will be overhead in the backend filesystem
code to manage xttrs.

However, if i try to delete the etc directory directly in the backend
(it was copied through glusterfs with self-heal on)
bash-3.1# time rm -rf /export/dir1/etc/

real    0m18.414s
user    0m0.000s
sys     0m0.132s
bash-3.1#

So there is significant overhead in the backend filesystem itself
when xattrs are involved.

Checking the overhead on open/close calls:
(here a.out opens, writes a byte, closes)

Selfheal is on:
bash-3.1# time find . -type f -exec /root/a.out {}  \;

real    0m1.529s
user    0m0.120s
sys     0m0.284s
bash-3.1#

Selfheal off:
bash-3.1# time find . -type f -exec /root/a.out {}  \;

real    0m0.577s
user    0m0.124s
sys     0m0.260s
bash-3.1#



There is  not much difference here. So setxattr/getxattr
does not take much time if xattrs are already existing on
he file. Hence there will be lot overhead only during create/unlink.

We will see if we can optimize anyway in the AFR code.
We have to note that backend system takes a lot
of time during create/delete which we dont have control
over. But still it is acceptable as there is not much overhead
during open/close/write calls.

Regards
Krishna

On 7/5/07, Anand Avati <avati at zresearch.com> wrote:
>
> Gerry,
> please use the write-behind translator on the client side (above AFR)
>
> thanks,
> avati
>
> 2007/7/4, Gerry Reno <greno at verizon.net>:
> >
> > In copying my /usr tree (4.9G) to a gluster client mount with a 4 brick
> > AFR with no other translators I see it is taking about 1 hr. 45 min.  Is
> > this normal performance?
> > Now this is with the bricks all on the same machine and same ext3
> > filesystem, but that seems like a long time even still.
> >
> > Gerry
> >
> >
> >
> >
> > _______________________________________________
> > Gluster-devel mailing list
> > Gluster-devel at nongnu.org
> > http://lists.nongnu.org/mailman/listinfo/gluster-devel
> >
>
>
>
> --
> Anand V. Avati
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>