7.1, mpt and slow writes

[Charles Sprickman]

On Thu, 29 Jan 2009, Richard Tector wrote:

> Charles Sprickman wrote:
>> Hello,
>> 
>> I think this needs a few more eyes:
>> 
>> http://lists.freebsd.org/pipermail/freebsd-scsi/2009-January/003782.html
>> 
>> In short, writes are slow, likely do to the write-cache being enabled on 
>> the controller.  The sysctl used in 6.x to turn the cache off don't seem to 
>> be in 7.x.
>
> I have two Dell 860's here also running 7.1-REL.
> A simple dd on one shows roughly 60MB/s writes to a mirror of 2 320GB disks 
> on what I'm assuming is the same LSI controller card (SAS5)
>
> richard at moses:~# cat /boot/loader.conf
> hw.mpt.enable_sata_wc=1
>
> Seems to work just fine for me.

Well, now I'm puzzled.  A "sysctl -a" shows no "hw.mpt." tree at all:

# sysctl -a|grep hw.mpt
#

It's a poor test, but:

# dd if=/dev/zero of=/jails/foo count=1M
1048576+0 records in
1048576+0 records out
536870912 bytes transferred in 144.830977 secs (3706879 bytes/sec)

# dd if=/jails/foo of=/dev/null
1048576+0 records in
1048576+0 records out
536870912 bytes transferred in 4.136582 secs (129786112 bytes/sec)

I added the tunable to loader.conf:

$ cat /boot/loader.conf
hw.mpt.enable_sata_wc=1

And still nothing in the sysctl output (there was on 6.4 on this same 
hardware, FWIW):

$ sysctl -a |grep hw.mpt
$

However, performance did improve:

# dd if=/dev/zero of=/jails/foo count=16M
16777216+0 records in
16777216+0 records out
8589934592 bytes transferred in 276.332753 secs (31085474 bytes/sec)

Any idea what happened to the sysctl?  Is there some other method to 
verify the loader tunable took (other than testing the throughput)?

I assume there's still no management tools for these controllers, right?

Thanks,

Charles

> Regards,
>
> Richard
>