Vinum & U320 SCSI, slower than UDMA100 IDE ?

[Sander Smeenk]

Quoting Greg 'groggy' Lehey (grog at freebsd.org):
> >Then I did a read test, like this:
> >>date;find . -type f|while read FILE;do cat "$FILE" > 
> >>/dev/null;done;date
> >I know it's not the most sophisticated test, but at least it shows that
> >on the IDE disk, this 'test' took 24 seconds to complete. On the RAID10
> >array it took a whopping 73 seconds to complete.
> You shouldn't expect any performance improvement with this kind of
> test, since you still need to access the data, and there's no way to
> do it in parallel.

I knew it wasn't the best way to test, but I did expect it to be at
least as fast as the same test on the same data on a IDE disk. And
luckily, you agree ;)

> >>  plex org striped 3841k
> You should choose a stripe size which is a multiple of the block size
> (presumably 16 kB).  Not doing so will have a minor performance
> impact, but nothing like what you describe here.

I might have misunderstood, but on the vinumvm.org website there is quite
a comprehensive discussion on stripesizes and they conclude that larger
stripesizes help increase throughput. They also discuss the size not
being a power of 2, because that might cause stripes to end up on the
same disk, which decreases performance...

> >>ahd1: PCI error Interrupt
> >>>>>>>>>>>>>>>>>>>>Dump Card State Begins <<<<<<<<<<<<<<<<<
> >>ahd1: Dumping Card State at program address 0x94 Mode 0x22
> This is possibly related.  Does it happen every time?

It did, until I compiled a new 4.9 kernel from the 4.9-RELEASE src/ tree
from CVS. (Thanks to Scott Long for pointing that out).
The driver for aic7xxx cards was fixed, and now the message is gone, and
the system is once again stable.

I didn't notice any real change in performance yet.

> The first thing to do is to find whether it's Vinum or the SCSI disks.
> Can you test with a single SCSI disk (of the same kind, preferably one
> of the array) instead of a single IDE disk?

I did some tests, this time with Bonnie++, on vinum, scsi, ide, and
vinum with big stripes and small stripes. I'm busy comparing them ;)

But still, I doubt if bonnie++ is a good test, and I have a hard time
interpreting the results. I can publish the results somewhere, in a
while.

Thanks,
Sander.
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