poor performances with Intel Raid Controller (iir)

[Mel]

On Friday 27 February 2009 04:14:49 Julien Cigar wrote:
> Hello,
>
> I've a machine with an integrated Intel RAID controller (U320) which
> uses the iir driver. I have two arrays, one RAID 1 with two disks and
> one RAID 5 with 8 disks. The disks are all Seagate 320MB/s. The system
> is running FreeBSD 7.0-RELEASE with 8 processors (2,40 Ghz) and 4GB or
> RAM.
>
> I have very poor performances, around ~50 MB/s, is it normal ?
>
> jcigar at bccm-it ~ % dd if=/dev/zero of=blah bs=10M count=100
> 100+0 records in
> 100+0 records out
> 1048576000 bytes transferred in 20.168689 secs (51990290 bytes/sec)
>
> Are there any tool to detect what could be the bottleneck(s) ?

dmesg to see if there's any indication about speeds.
camcontrol inquiry bus:lun to get capabilities, including transfer rate
gstat to see I/O transactions.

You might not be able to see past the RAID controller, to rule out the actual 
disks. Also, bs > 2M usually degrades performance, start with 1M and go up.

-- 
Mel

Problem with today's modular software: they start with the modules
    and never get to the software part.