[9fans] DPT PM2041W observations

[G. David Butler gdb@dbSystems.com]

>So why does this 4th generation card with tag queueing support
>run slower than the 1st generation design that is over 10 years
>old?

Some further info.  Having enabled tag queueing I went back to
do other benchmarks since the sequential write performance is
now in the same ballpark.  Tag queueing makes a big difference
everywhere!  Random reads and writes are much faster than without
tags.  In fact, the overall result is that the DPT, with tag
queueing, is quite a bit faster than the 154x.  Without tag
queueing the 154x is faster.

Now should I investigate the cache/raid add-on card?  I currently
do "software" mirroring across controllers to handle controller
failure.  Most drives now have advertised MTBFs of 1,000,000 hours.
The 154x has a MTBF of 300,000.  What is the DPT's?

I like the idea of mirroring on the controller so the data only
passes over the ISA bus once.  Is this true?  What is the minimum
configuration for the 2041W to do RAID-1?  What is the MTBF of
that configuration?  In that configuration is there any caching?
Does the cache honor DPO and FUA in the extended read/write
SCSI commands?

Is there a current technical reference manual available?

Thanks for any info.

David Butler
gdb@dbSystems.com