> 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
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