Markus Kovero <Markus.Kovero <at> nebula.fi> writes:
>
>
> > Sync was disabled on the main pool and then let to inherrit to everything
else. The > reason for disabled
> this in the first place was to fix bad NFS write performance (even with > Zil
on an X25e SSD it was under 1MB/s).
> > I've also tried setting the logbias to throughput and latency but they both
perform > around the same level.
>
> > Thanks
> > -Matt
>
> I believe you're hitting bug "7000208: Space map trashing affects NFS write
throughput". We also did, and
> it did impact iscsi as well.
>
> If you have enough ram you can try enabling metaslab debug (which makes
problem vanish);
>
> # echo metaslab_debug/W1 | mdb -kw
>
> And calculating amount of ram needed:
>
> /usr/sbin/amd64/zdb -mm <poolname> > /tmp/zdb-mm.out
>
> awk '/segments/ {s+=$2}END {printf("sum=%d\n",s)}' zdb_mm.out
>
> 93373117 sum of segments
> 16 VDEVs
> 116 metaslabs
> 1856 metaslabs in total
>
> 93373117/1856 = 50308 average number of segments per metaslab
>
> 50308*1856*64
> 5975785472
>
> 5975785472/1024/1024/1024
> 5.56
>
> = 5.56 GB
>
> Yours
> Markus Kovero
>
We are running Solaris Express 11. We hit this same problem when we crossed 80%
usage on our mirror pool.
Write performance dropped to 3-8 MB/sec on 48 mirror sets!
echo metaslab_debug/W1 | mdb -kw resolves problem instantly.
What are the ramifications of running this command?
Thanks
- Jamie
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