On Jul 4, 2010, at 8:08 AM, Ian D wrote:
> >Ok... so we've rebuilt the pool as 14 pairs of mirrors, each pair having one
> >disk in each of the two JBODs. >Now we're getting about 500-1000 IOPS
> >(according to zpool iostat) and 20-30MB/sec in random read on a big
> >>database. Does that sounds right?
> >Seems right, as Erik said. Btw, do you use SSDs for L2ARC/SLOG here? If not,
> >that might help quite a bit.
>
> I have 8x 100GB SLC SDDs (the Samsung ones that Dell sells) for the L2ARC and
> 2x 4GB DDRDrive X1s in mirror for the SLOG. The server also has 128GB of
> RAM, I can see 100GB+ are used for the ARC. I'll also double the RAM to
> 256GB and add 4 more SSDs (total 1.2TB) for the L2ARC once I'm ready to go to
> production. I will eventually connect total of 75 SATA drives and 84 SAS 15K
> drives to it, I just want to make sure that I get the most of what I have.
> When I run a dozen large SQL queries at once (they can take >10 mins) I
> consistently get 300-1000 IOPs and 10-30MB/sec from the pool (according to
> zpool iostat).
>
> What I don't understand is why, when I run a single query I get <100 IOPS and
> <3MB/sec. The setup can obviously do better, so where is the bottleneck? I
> don't see any CPU core on any side being maxed out so it can't be it...
>
> The database is MySQL, it runs on a Linux box that connects to the Nexenta
> server through 10GbE using iSCSI.
Check your Nagle algorithm setting. Since you didn't mention what OS you are
running, it is a little bit hard for us to guess and give you the command. For a
typical OpenSolaris based distribution try looking at the output of:
ndd /dev/tcp tcp_naglim_def
If the value is not 1, then try setting it to 1. For NexentaStor users, this
is easily
changed in the GUI under the Settings -> Preferences -> Network form. For
OpenStorage users, it should be set by default.
-- richard
--
Richard Elling
rich...@nexenta.com +1-760-896-4422
ZFS and NexentaStor training, Rotterdam, July 13-15, 2010
http://nexenta-rotterdam.eventbrite.com/
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