performance with LSI SAS 1064

[Scott Long]

54MB/s is reasonable for 10k 2.5" disks.  You might be able to squeeze
some more performance by upgrading to FreeBSD 7.0.  I _do_not_ recommend
playing with the queue depth controls unless your console logs are
getting quickly filled with messages about it.

Scott


Lutieri G. wrote:
> 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
>>
>>
>>
>>
>>
> 
>