Check your gstat with -dp so you also see deletes, it may be that your
drives have a very slow TRIM.
On 28/11/2016 17:54, Eugene M. Zheganin wrote:
Hi,
recently we bough a bunch of "Sandisk CloudSpeed Gen. II Eco Channel"
disks (the model name by itself should already made me suspicious) for
using with zfs SAN on FreeBSD, we're plugged them into the LSI SAS3008
and now we are experiencing the performance that I would call
"literally awful". I'm using already some of the zfs SANs on FreeBSD
with Intel/Samsung SSD drives, including the LSI SAS3008 controller,
but never saw anything like this (and yes, these are all SSDs):
dT: 1.004s w: 1.000s
L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name
75 472 78 367 104.4 12 1530 94.8 113.4| da0
75 475 81 482 79.2 12 1530 94.5 113.1| da1
69 490 96 626 106.9 12 1530 124.9 149.4| da2
75 400 72 382 51.5 10 1275 93.7 93.4| da3
0 0 0 0 0.0 0 0 0.0 0.0| da4
75 400 72 382 55.0 10 1275 93.9 93.7| da5
2 3975 3975 24020 0.3 0 0 0.0 21.0| da6
0 3967 3967 24144 0.3 0 0 0.0 21.4| da7
1 3929 3929 24259 0.3 0 0 0.0 21.6| da8
0 3998 3998 23933 0.3 0 0 0.0 21.2| da9
0 0 0 0 0.0 0 0 0.0 0.0| da10
0 4037 4037 23710 0.2 0 0 0.0 21.3| da11
0 0 0 0 0.0 0 0 0.0 0.0| da12
0 0 0 0 0.0 0 0 0.0 0.0| da13
0 0 0 0 0.0 0 0 0.0 0.0| da14
0 0 0 0 0.0 0 0 0.0 0.0| da15
0 0 0 0 0.0 0 0 0.0 0.0| da16
Disks are ogranized in the raidz1 pools (which is slower than the
raid1 or 10, but, considering the performance of SSDs, we got no
problems with Intel or Samsung drives), the controller is flashed with
last firmware available (identical controller with Samsung drives
performs just fine). Disks are 512e/4K drives, and "diskinfo
-v"/"camcontrol identify" both report that they have 4K
stripersize/physical sector. Pools are organized using dedicated
disks, so, considering all of the above, I don't see any possiblity to
explain this with the alignment errors. No errors are seen in the
dmesg. So, right at this time, I'm out of ideas. Everything point that
these Sandisk drives are the roort of the problem, but I don't see how
this is possible- according to the various benchmarks (taken, however,
with regular drives, not "Channel" ones, and so far I haven't figured
out what is the difference between "Channel" and non-"Channel" ones,
but they run different firmware branches) they have to be okay (or
seem so), just the ordinary SSD.
If someone has the explanation of this awful performance, please let
me know.
Thanks.
Eugene.
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