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Re: NFS problems (also contains RAID report!) - LONG!
udif@bigfoot.com (Udi Finkelstein) wrote:
> -----------------------------------------------------------------------
> My system 3 IBM disks, 22GB ATA 7200RPM, adn an intel server motherboard
> (T440BX).
>
> Installed stock RH 6.0. 3 disks installed as /dev/hda, /dev/hdb,
> /dev/hdc,
> with ATAPI CDROM as /dev/hdd.
> (1) The kernel reports that the BIOS says that /dev/hda is PIO, while
> /dev/hdb
> and d/ev/hdc use DMA. weired.
BIOS settings, probably?
> (2) The kernel reports that /dev/hda and /dev/hdb use 2748/255/63
> geometry,
> while /dev/hdc is 43800/16/63. Even more weired.
I've seen it several times, too, that the LBA is not recognized by the
kernel for the second IDE channel, probably, buggy BIOS.
> measured performance with hdparm -t /dev/hd[abc] and got a disappointing
> 2.3MB/s.
Forget about hdparm, it's a toy (I mean, hdparm -t). Use bonnie.
> Solved with hdparm -d 1 /dev/hd[abc]. speed now goes to 16MB/s.
> somehow this works even for large blocks. The command:
> time dd if=/dev/hda of=/dev/null count=1024 bs=131072
> takes 7-8 seconds, yielding 16MB/s actual disk throughput !! never
> expected
> this!
> The DMA setting above is kept somwehere on a file, as it retains the
> value
> even after reboot.
?? I hardly believe this. Maybe, in the BIOS?
> Now comes the RAID part. I made a linear raid
Why not RAID0? Generally, you'd get much better perfromance and could tune
it to your specific needs. I've once done more or less extensive benchmarks;
see http://plasma-gate.weizmann.ac.il/~fnevgeny/raid/raid0.gif. Also,
comparison of performance of different (software) RAID levels:
http://plasma-gate.weizmann.ac.il/~fnevgeny/raid/raid.gif.
Regards,
Evgeny
--
____________________________________________________________
/ Evgeny Stambulchik <fnevgeny@plasma-gate.weizmann.ac.il> \
/ Plasma Laboratory, Weizmann Institute of Science, Israel \ \
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