performance issues: linux aic7xxx, 29160, Radion IFT-7200

[Justin T. Gibbs]

>"Justin T. Gibbs" wrote:
>> 
>> >Hello again,
>> 
>> I wonder if for some reason we have disconnection disabled?  I get much
>> better performance than that talking to a plain old 10K RPM disk.  Can
>> you go into aic7xxx.c, search for ahc->user_discenable and print out the
>> contents of that variable?
>
>linux-2.4.18/drivers/scsi/aic7xxx/aic7xxx.c
>(not-patched, so this is version 6.2.4)
>line 4547
>ahc->user_discenable = discenable;

I meant insert a printf to display the actual value of the variable
after it is set. 8-)

>same in 2.4.16 ( I guess that's the same version so that would make
>sense, of course...)
>
>after patching the 2.4.18 sources for aic7xxx 6.2.5 the file names in
>drivers/scsi/aic7xxx/ are different. Which one should I be looking at
>there?

aic7xxx_core.c

>> >Is there something else I can do to try to get better performance with
>> >the new driver?
>> 
>> If I understood why the performance was bad, I'd tell you. 8-)
>> Any chance you can rent a SCSI bus analyzer for a day and capture
>> some traces?
>
>umm, I'll check with the boss, but I doubt it. Where would a person rent
>such a thing?

Check the yellow pages under electronic test equipment rentals.  This
is the same place you'd go to rent a logic analyzer or scope for a few
days.  You could also see if Verisys, Ancot, or Innotec, would allow
you to "demo" their SCSI analyzer products.

>Ok, so probably very few people would ever care only about sequential
>performance? We will have up to 4 streams of current broadcasts writing
>to disk and potentially 'many' users streaming via http or copying via
>http or smb from the archive. And for a time, someone will be copying
>the past archives off CDs onto the raid via a samba share.
>
>Can hdparm be used to measure non-sequential performance? is there a way
>to quantify this?

hdparam is a very poor benchmark in general.  Doug Ledford lists some
other benchmarking tools on his web site that might be of interest,
but I have never tried them personally.

I'm still very perplexed by the difference in performance.  Can you
also provide a cat of /proc/scsi/aic7xxx/0 <- or whatever bus number
happens to have this device on it.

--
Justin

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