Can someone explain this result?

devsk devsku at gmail.com
Sun May 8 03:15:54 EDT 2011


For me, idling does not make any difference. It never goes back the
time it took the first time. I think your issue may be different. RAM
is not an issue for me because I have 12GB of RAM and about 6GB is
free at this time.

# time find rsynced/|wc -l
384736

real    1m50.919s
user    0m0.342s
sys     0m4.496s

-devsk


On May 7, 11:24 pm, ahamilto <ahami... at tjhsst.edu> wrote:
>  I have noticed similar behavior, also with a RAIDZ1 non-rootfs pool
>  with dedup and compression both enabled.  If I run a large rsync
>  operation to or from the pool, the transfer will get slower and slower
>  over time until eventually (after a few hours or so) it will almost
>  grind to a halt.  If I stop the rsync and let the server idle for a
>  while, when i continue, performance is back up.  I have noticed that
>  while the rsync is running, server load and memory usage will steadily
>  climb until the server is using all of the memory (6GB) and the load
>  average hovers around 13.
>
>  If anyone needs any more information on this setup, please let me know.
>
>  --ahamilto
>
>  On Sat, 7 May 2011 22:46:40 -0700 (PDT), devsk <dev... at gmail.com>
>
>
>
>
>
>
>
>  wrote:
> > # time find rsynced/|wc -l
> > 384736
>
> > real    0m50.615s
> > user    0m0.350s
> > sys     0m19.404s
>
> > # time find rsynced/|wc -l
> > 384736
>
> > real    2m5.708s
> > user    0m0.315s
> > sys     0m5.185s
>
> > # time find rsynced/|wc -l
> > 384736
>
> > real    1m53.062s
> > user    0m0.350s
> > sys     0m4.418s
>
> > The FS is idle at this time and so is the pool. This is not rootfs.
> > Its a RAIDZ1 pool with dedup and compression on. There is an SSD
> > configured as a cache device.
>
> > How is it possible that when I run the first time, I get the fastest
> > time while subsequent runs are slower by more than half. I am
> > baffled.
> > And this is not the first time ZFS on Linux has done this: this has
> > been seen multiple times now because it did this when I was running
> > ZFS rootfs on my laptop.
>
> > -devsk



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