Poor write performance with LSI 320-2 on 6.1-STABLE

Scott Long scottl at samsco.org
Fri Sep 29 09:36:35 PDT 2006


Albert Chin wrote:
> I have an Intel S875PWP1 motherboard with a Pentium4 CPU at 2.40GHz. PCI
> bus is 33Mhz, 32-bit. I recently purchased an LSI 320-2/128MB on eBay
> (though the card really looks like a PERC4/DS) and just ran some
> bonnie++ tests on a RAID 1 array between two U320 drives for the first
> channel and on a RAID 0 array between one U320 drive for the second
> channel. The 320-2 has the latest LSI firmware, 1L47.
> 
[...]
> 
> I don't understand how #1 gives 16MB/s (RAID 1) while #3 gives only
> 17MB/s. I'd expect #3 to be about x2 the performance of #1.

> 
> The arrays are configured with "write-thru" write policy, "adaptive"
> read policy, and "cachedio" cache policy.

In LSI terms, "write-thru" means, "write cache is turned off".  With
that set, performance becomes very consistently describable as "poor",
as your tests demonstrate.  Linux can get around this a little bit in
benchmarks by using larger I/O sizes than FreeBSD (FreeBSD is limited to
128K max, while Linux is not).

These are very speedy cards once you put them into their intended
configuration.  With some decent SCSI disks and a PCI-X bus, it
performs quite well.  However, I'm actually kinda surprised that the
card works at all in your 5V slot.

Scott


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