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

[Albert Chin]

On Fri, Sep 29, 2006 at 10:33:14AM -0600, Scott Long wrote:
> 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).

If you don't have the battery backup, "write-thru" might be a bit of a
problem :)

> 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.

Yeah, but we have a few of these mobos so figured we might as well
reuse them. And, we got the 320-2 for cheap.

According to http://lsionline2.lsil.com/esupport/esupportlsi/consumer/esupport.asp?hotid=bf88d26d-7205-4bcd-a542-d2a9b4af2b4e&number=1&nShowFacts=&nShowCause=&nShowChange=&nShowAddInfo=&activepage=statement.asp&bForceMatch=False&strCurrentSymptom=&searchtype=normal&searchclass=QuickSearch&bnewsession=True&selecttype=match:
  Q. Will a 64-bit PCI MegaRAID controller work in a 32-bit PCI slot (or
     vise versa)? Will a 64-bit controller work in a PCI-X slot (or vise
     versa)?
  A. Yes. If the controller fits in the PCI or PCI-X slot, the
     MegaRAID controller will operate. However, the performance of a
     64-bit controller will be degraded when placed in a 32-bit slot.

-- 
albert chin (china at thewrittenword.com)