I've got a pool which I'm currently syncing a few hundred gigabytes to
using rsync. The source machine is pretty slow, so it only goes at
about 20 MB/s. Watching "zpool iostat -v local-space 10", I see a
pattern like this (trimmed to take up less space):
capacity operations bandwidth
pool used avail read write read write
---------- ----- ----- ----- ----- ----- -----
local-space 251G 405G 0 143 51 17.1M
mirror 251G 405G 0 143 51 17.1M
c1d0s6 - - 0 0 0 0
c0d0s6 - - 0 137 0 17.1M
local-space 252G 404G 1 163 2.55K 17.6M
mirror 252G 404G 1 163 2.55K 17.6M
c1d0s6 - - 0 145 6.39K 16.7M
c0d0s6 - - 0 150 38.4K 17.6M
local-space 253G 403G 0 159 511 16.9M
mirror 253G 403G 0 159 511 16.9M
c1d0s6 - - 0 340 0 41.0M
c0d0s6 - - 0 145 12.8K 16.9M
local-space 253G 403G 0 135 511 16.2M
mirror 253G 403G 0 135 511 16.2M
c1d0s6 - - 0 484 0 60.4M
c0d0s6 - - 0 130 0 16.2M
local-space 253G 403G 0 125 0 15.4M
mirror 253G 403G 0 125 0 15.4M
c1d0s6 - - 0 471 0 59.0M
c0d0s6 - - 0 123 0 15.4M
local-space 253G 403G 0 139 0 16.2M
mirror 253G 403G 0 139 0 16.2M
c1d0s6 - - 0 474 0 59.3M
c0d0s6 - - 0 129 0 16.2M
local-space 253G 403G 0 139 51 17.1M
mirror 253G 403G 0 139 51 17.1M
c1d0s6 - - 0 3 6.39K 476K
c0d0s6 - - 0 137 0 17.1M
local-space 253G 403G 0 144 0 18.1M
mirror 253G 403G 0 144 0 18.1M
c1d0s6 - - 0 0 0 0
c0d0s6 - - 0 144 0 18.1M
local-space 253G 403G 0 146 0 18.1M
mirror 253G 403G 0 146 0 18.1M
c1d0s6 - - 0 0 0 0
c0d0s6 - - 0 144 0 18.1M
local-space 253G 403G 0 156 0 19.3M
mirror 253G 403G 0 156 0 19.3M
c1d0s6 - - 0 0 0 0
c0d0s6 - - 0 154 0 19.3M
local-space 253G 403G 0 152 0 19.1M
mirror 253G 403G 0 152 0 19.1M
c1d0s6 - - 0 0 0 0
c0d0s6 - - 0 152 0 19.1M
local-space 253G 403G 0 158 0 19.1M
mirror 253G 403G 0 158 0 19.1M
c1d0s6 - - 0 0 0 0
c0d0s6 - - 0 152 0 19.1M
local-space 253G 403G 0 150 0 18.5M
mirror 253G 403G 0 150 0 18.5M
c1d0s6 - - 0 0 0 0
c0d0s6 - - 0 147 0 18.5M
local-space 253G 403G 0 155 0 19.4M
mirror 253G 403G 0 155 0 19.4M
c1d0s6 - - 0 0 0 0
c0d0s6 - - 0 155 0 19.4M
The interesting part of this (as far as I can tell) is the rightmost
column; the write speeds of the second disk stay constant at about 20
MB/s, and the first disk fluctuates between zero and 60 MB/s. Is this
normal behavior? Could it indicate a failing disk? There's nothing
in `fmadm faulty', `dmesg', or `/var/adm/messages' that would indicate
an impending disk failure, but this behavior is strange. I'm using
rsync-3.0.1 (yes, security fix is on the way) on both ends, and no NFS
involved in this. rsync is writing 256k blocks. `iostat -xl 2' shows
a similar kind of fluctuation going on.
Any suggestions what's going on? Any other diagnostics you'd like to
see? I'd be happy to provide them.
Thanks!
Will
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