LSI SAS2008 performance with mps(4) driver

[Rumen Telbizov]

Dustin,


Thanks; It's good to know that it's at least possible to make this work in
> some instances.
>

It does.


Unfortunately, our SAS2008 controller is integrated with the logic board (a
> SuperMicro X8DT6) connected to a SAS-113TQ backplane.


Well I forgot to mention that those 9211-8i's that I have were actually used
on X8DT6-F motherboard that I purchased
specifically so that I use the built-in controller and save one external.
Well listen ... the chip on this mother board is SAS2008
and is exactly the same as far as I can tell. I did go ahead and flashed it
too with the latest firmware - 9.00 and it did make a
difference for me when playing with the SAS expanders.


> It's not so much of an expander; there are two breakout cables that go from
> the SFF8087 connectors to individual SATA connectors for each drive on the
> backplane.


Interesting. It is indeed a direct attached backplane then. Nevertheless I
wouldn't be surprised if there's another form of
incompatibility with some of the direct attached backplanes.


> I've spoken with LSI, and (unsurprisingly) they are unable to provide
> firmware for chips which are integrated in 3rd party devices. SuperMicro
> also doesn't have any particularly recent updates - the newest I could find
> was from last August.
>

I think version 9.00 will be released any moment now.



> If this is indeed an issue with the onboard SAS2008 hardware/firmware, I'm
> probably going to have to spring for a separate controller card in the short
> term. :/
>
>        - .Dustin
>
> On Mar 10, 2011, at 10:09 PM, Rumen Telbizov wrote:
>
> > Hello Dustin,
> >
> > I've been testing this SAS2008 LSI chip (on a LSI 9211-8i) for the last
> month or so and I can say
> > that it makes a pretty good HBA but there are indeed a few caveats you
> might need to be aware of.
> > In support of that - tonight I finished a FreeBSD 8.2-STABLE machine with
> 2 x 24 disk chassis (each with
> > a 3Gbit expander) = 48 x 2TB SATA RE4-GP disks in 6 x 8disk raidz2 and I
> am able to squeeze out 900MB/s
> > write and 1200 MB/s read in a sequential (single dd) manner. The limit
> here is the backplane speed.
> >
> > So back to your problem:
> >
> > 1) What kind of backplane are you using: please specify the exact model.
> Is it a SAS expander or direct attached?
> > 3Gbit/s or 6Gbit/s?
> > 2) What kind of disk controller exactly are you using? More importantly
> what kind of firmware does it have?
> >
> > Those two are very important. In my case it turned out that if I was
> connecting SAS2008 chips
> > to pretty much every kind of SuperMicro SAS expander backplanes (tried
> against 826EL26, 836E1, 846E1) I was
> > getting around 200-300MB/s read/write speeds (FreeBSD and Linux). Direct
> attached backplanes (826A) worked fine.
> > At the end it turned out that it was some sort of a problem with the LSI
> firmware (version 8.00 in my case) and I was given
> > to try version 9.00 (soon to be released) which completely solved the
> problem. Contact LSI support (very high quality) if you want to try this
> firmware.
> >
> > I can't seem to get any better performance than about 250MB/s writes
> through the controller. I'm testing with a zpool of six 250MB magnetic SATA
> disks, doing a couple of concurrent sequential writes with dd:
> >
> > dd bs=128k if=/dev/zero of=/datadisk/zero1 &
> > dd bs=128k if=/dev/zero of=/datadisk/zero2 &
> >
> >
> > 3) What kind of zpool raid level do you have those disks organized in?
> > 4) Running two parallel dd's on the same pool will actually turn the game
> into no-so-sequential type and more of a random access.
> > Please try the following and paste results here:
> > 4.1) dd if=/dev/zero of=/datadisk/zero1 bs=1M count=50000 (only one dd
> and use a file size larger than your memory)
> > 4.2) Destroy the zpool (if you have no useful data on it of course) and
> try dd against each and every disk individually.
> > So something like:
> > dd if=/dev/zero of=/dev/da0 bs=1M count=50000
> > dd if=/dev/da0 of=/dev/null bs=1M count=50000
> > monitor throughput with gstat -f da0 or I can send you a simple C program
> that I wrote which resembles dd but
> > prints stats every second.
> >
> > On a related note I also experienced very slow read speeds (200MB/s) with
> the above mentioned configuration and after enabling
> > prefetch (I used to set it to disabled as per Jeremy Chadwick's advise)
> everything went back to normal - so keep it in mind.
> >
> > Cheers,
> > Rumen Telbizov
> >
> > --
> > Rumen Telbizov
> > http://telbizov.com
>
>


-- 
Rumen Telbizov
http://telbizov.com