Sandisk CloudSpeed Gen. II Eco Channel SSD vs ZFS = we're in hell
Steven Hartland
killing at multiplay.co.uk
Mon Nov 28 18:07:03 UTC 2016
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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