performance with LSI SAS 1064

[Lutieri G.]

This is my disks:

Seagate Savvio(ST913401ss) 10K.1 SAS 3Gb/s 73-GB Hard Drive. In the
manual file i found this information:

Queue tagging (up to 64 queue tags supported)

Is this the max # for setting using camcontrol?! syntax like this:
camcontrol tags da0 -N 64 ??

2007/8/30, Eric Anderson <anderson at freebsd.org>:
> Scott Long wrote:
> > Lutieri G. wrote:
> >> 2007/8/30, Eric Anderson <anderson at freebsd.org>:
> >>> I'm confused - you said in your first post you were getting 3MB/s, where
> >>>   above you show something like 55MB/s.
> >> Sorry! using blogbench i got 3MB/s and 100% busy. Once is 100% busy i
> >> thinked that 3MB/s is the maximum speed. But i was wrong...
> >
> > %busy is a completely useless number for a anything but untagged,
> > uncached disk subsystems.  It's only an indirect measure of latency, and
> > there are better tools for measuring latency (gstat).
> >
> >>> You didn't say what kind of disks, or how many, the configuration, etc -
> >>> so it's hard to answer much.  The 55MB/s seems pretty decent for many
> >>> hard drives in a sequential use state (which is what dd tests really).
> >>>
> >> SAS disks. Seagate, i don't know what is the right model of disks.
> >>
> >> Ok. If 55Mb/s is a decent speed i'm happy. I'm getting problems with
> >> squid cache and maybe should be a problem related with disks. But...
> >> i'm investigating and discharging problems.
> >>
> >>
> >>> Your errors before were probably caused because your queue depth is set
> >>> to 255 (or 256?) and the adapter can't do that many.  You should use
> >>> camcontrol to reduce it, to maybe 32.  See the camcontrol man page for
> >>> the right usage.  It's something that needs setting on every boot, so a
> >>> startup file is a good place for it maybe.
> >>>
> >> Is there any way of get the right number to reduce?!
> >>
> >
> > If you're seeing erratic performance in production _AND_ you're seeing
> > lots of accompanying messages on the console about tag depth jumping
> > around, you can use camcontrol to force the depth to a lower number of
> > you're choosing.  This kind of problem is pretty rare, though.
>
> Scott, you are far more of a SCSI guru than I, so please correct me if
> this is incorrect.  Can't you get a good estimate, by knowing the queue
> depth of the target(s), and dividing it by the number of initiators?  So
> in his case, he has one initiator, and (let's say) one target.  If the
> queue depth of the target (being the Seagate SAS drive) is 128 (see
> Seagate's paper here:
> http://www.seagate.com/staticfiles/support/disc/manuals/enterprise/savvio/Savvio%2015K.1/SAS/100407739b.pdf
> ), then he should have to reduce it down from 25[56] to 128, correct?
>
> With QLogic cards connected to a fabric, I saw queue depth issues under
> heavy load.
>
> Eric
>
>
>
>
>


-- 
Att.
Lutieri G. B.