Re: "Misbehaving" hard disk or weird RAIDframe problem

[Matthias Scheler <tron%zhadum.org.uk@localhost>]

On 12 Jan 2009, at 19:12, Greg Oster wrote:
> What happens if you do both of the above dd's simultaneously?

No problems.

> Do you see the same levels of performance, or does it drop off
> drastically?

Both harddisks deliver data at over 75MB/s.

> Is the write cache turned off on one of the drives?

Aaaaaaaaaaaaaaaaaargh!

Yes, of course. That's it. And the really annoying bit is that
I knew that. When that disk was the only disk in the system
I had the following bit in "/etc/rc.local":

echo -n "Turning on disk write-cache ... "
dkctl wd0 setcache rw && echo "done."

But I commented it out when I replaced that disk with two
newer hard disks. Running it immediately fixes the problem:

tron@colwyn:~tron#dkctl wd2 setcache rw
tron@colwyn:~tron#dd if=/dev/zero of=/dev/rwd2d bs=1m count=256256+0  
records in
256+0 records out
268435456 bytes transferred in 3.453 secs (77739778 bytes/sec)

        Thanks a great lot

--
Matthias Scheler                           http://zhadum.org.uk/