Bad disk performance under ultrix
ztion
I just got a FDDI card (DEFTA) for my DECstation 5000/260 running
ultrix 4.5. When I tried it out with ftp I only got a transfer rate of
1,9 MB/s to 2 MB/s. This surprised me a bit, so I investigated. With
netperf I got much better results, 40mbit/s if I ran netserver on the
ultrix machine and netperf on the pc, and 48mbit/s if I did it the
other way around.
So I suspected perhaps the disk was running slow, and it seems I was
correct. See this result of bonnie:
-------Sequential Output-------- ---Sequential Input--
--Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block---
--Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU
/sec %CPU
100 1834 97.6 2595 50.9 638 11.4 1809 95.9 2886 34.3
59.2 14.1
It is a 9 GB, 7200 rpm, fairly modern disk, so I think it should run
very near the 5 MB/s limit of the scsi interface in the DECstation.
Is there something you can tune to make it run faster?
ztion
I used tunefs -a 8 and ncftp instead of the standard ultrix ftp, and
now I get about 2,4 mb/s. I guess I should be happy with that since
this is a pretty old machine.
But it would still be interesting if anyone has any ideas on how to
make it even faster.
Gregg Economou
well, youre not going to get too much more out of the onboard asc..
remember, it's 10 MHz narrow scsi, with a maximum throughput of 10mb/s..
take into account overhead for pushing commands and out of band info over
the scsi bus, and your max goes down to 8-9. put a reasonably fast
modern scsi disk on it, and you might see 7 or 8. now, consider that ftp
is slow, that tcp is slow... that it all has to to pushed through bus to
the kernel to userland back to kernel back to the bus, and you start to
see where the performance goes. testing the disk alone, assuming its a faster
modern disk, will probably show streaming speeds of 8 megs/sec. testing
the network alone will likewise show speeds of 4 or so megs/sec on the fddi.
shovelling the bits around more realisatically, and that 2.4 is close to the
best you'll get. i've had similar experience with my decstations (and a
DEC3000/600 alpha) on an fddi ring. NetBSD gave slightly better performance
than ultrix, you might want to take that route, too..
isildur
ztion
> well, youre not going to get too much more out of the onboard asc..
> remember, it's 10 MHz narrow scsi, with a maximum throughput of 10mb/s..
> take into account overhead for pushing commands and out of band info over
> the scsi bus, and your max goes down to 8-9. put a reasonably fast
> modern scsi disk on it, and you might see 7 or 8.
Actually I'm pretty sure the default scsi interface on a DECstation is
old 5 mhz / 5 MB/s. But there was a turbochannel card you could buy
that gave you 2 fast-scsi interfaces. It would be pretty neat to have
one of those, but unfortunately I don't have any slots left: 2 slot
PMAG-E and FDDI card. Time to get a turbochannel extender box? ;)
But yeah, I guess I should be satisfied with the speed I got now.
Bonnie reported 3,5 MB/s reading blockwise, and 3 MB/s writing
blockwise. When it is writing 1 byte at a time there is 99% cpu usage,
so I guess that's a pretty big bottleneck. Many programs don't write in
large blocks.
> now, consider that ftp
> is slow, that tcp is slow... that it all has to to pushed through bus to
> the kernel to userland back to kernel back to the bus, and you start to
> see where the performance goes. testing the disk alone, assuming its a faster
> modern disk, will probably show streaming speeds of 8 megs/sec. testing
> the network alone will likewise show speeds of 4 or so megs/sec on the fddi.
> shovelling the bits around more realisatically, and that 2.4 is close to the
> best you'll get. i've had similar experience with my decstations (and a
> DEC3000/600 alpha) on an fddi ring. NetBSD gave slightly better performance
> than ultrix, you might want to take that route, too..
At least it is faster than the 100 mbit ethernet card in my
sparcstation 5 running sunos 4.
I found some fastnet patches for ultrix 4.2a that supposedly sped up
the network, but I guess they already merged that in ultrix 4.5. It was
some faster checksum algorithms and such.
I have a dec3000/300x I could theoreticaly try it in, but I haven't
been able to get it to boot. I got it for free, and I guess something
must have broke on the busride home. It fails after the second memory
test, when it enables the bcache, so perhaps something is busted on the
cpucard.