That's interesting - 'zpool iostat' shows quite small read volume to any pool
however if I run 'zpool iostat -v' then I can see that while read volume to a
pool is small, read volume to each disk is actually quite large so in summary I
get over 10x read volume if I sum all disks in a pool than on pool itself.
These data are consistent with iostat. So now even zpool claims that it
actually issues 10x (and more) read volume to all disks in a pool than to pool
itself.
Now - why???? It really hits performance here...
bash-3.00# zpool iostat -v p1 1
capacity operations bandwidth
pool used avail read write read write
------------------------- ----- ----- ----- ----- ----- -----
p1 749G 67.2G 58 90 878K 903K
raidz 749G 67.2G 58 90 878K 903K
c4t500000E011909320d0 - - 15 40 959K 87.3K
c4t500000E011909300d0 - - 14 40 929K 86.5K
c4t500000E011903030d0 - - 18 40 1.11M 86.8K
c4t500000E011903300d0 - - 13 32 823K 77.7K
c4t500000E0119091E0d0 - - 15 40 961K 87.3K
c4t500000E0119032D0d0 - - 14 40 930K 86.5K
c4t500000E011903370d0 - - 18 40 1.11M 86.8K
c4t500000E011903190d0 - - 13 32 828K 77.8K
c4t500000E011903350d0 - - 15 40 964K 87.3K
c4t500000E0119095A0d0 - - 14 40 934K 86.5K
c4t500000E0119032A0d0 - - 18 40 1.11M 86.8K
c4t500000E011903340d0 - - 13 32 821K 77.7K
------------------------- ----- ----- ----- ----- ----- -----
capacity operations bandwidth
pool used avail read write read write
------------------------- ----- ----- ----- ----- ----- -----
p1 749G 67.2G 49 44 897K 1.02M
raidz 749G 67.2G 49 44 897K 1.02M
c4t500000E011909320d0 - - 17 25 1.05M 96.4K
c4t500000E011909300d0 - - 15 25 972K 96.2K
c4t500000E011903030d0 - - 20 25 1.25M 96.3K
c4t500000E011903300d0 - - 14 25 853K 91.2K
c4t500000E0119091E0d0 - - 16 25 1017K 96.7K
c4t500000E0119032D0d0 - - 15 25 955K 96.7K
c4t500000E011903370d0 - - 19 25 1.21M 96.6K
c4t500000E011903190d0 - - 13 25 843K 91.0K
c4t500000E011903350d0 - - 16 25 1001K 96.5K
c4t500000E0119095A0d0 - - 15 25 974K 96.3K
c4t500000E0119032A0d0 - - 20 25 1.22M 96.5K
c4t500000E011903340d0 - - 14 25 855K 90.7K
------------------------- ----- ----- ----- ----- ----- -----
^C
bash-3.00#
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