Re: Zlatko's I/O slowdown status

[Simon Kirby]

On Fri, Nov 02, 2001 at 09:14:14PM +0100, Zlatko Calusic wrote:

> Thank God, today it is finally solved. Just two days ago, I was pretty
> sure that disk had started dying on me, and i didn't know of any
> solution for that. Today, while I was about to try your patch, I got
> another idea and finally pinpointed the problem.
> 
> It was write caching. Somehow disk was running with write cache turned
> off and I was getting abysmal write performance. Then I found hdparm
> -W0 /proc/ide/hd* in /etc/init.d/umountfs which is ran during shutdown
> but I don't understand how it survived through reboots and restarts!
> And why only two of four disks, which I'm dealing with, got confused
> with the command. And finally I don't understand how I could still got
> full speed occassionaly. Weird!
> 
> I would advise users of Debian unstable to comment that part, I'm sure
> it's useless on most if not all setups. You might be pleasantly
> surprised with performance gains (write speed doubles).

Aha!  That would explain why I was seeing it as well... and why I was
seeing errors from hdparm for /dev/hdc and /dev/hdd, which are CDROMs.

Argh. :)

If they have hdparm -W 0 at shutdown, there should be a -W 1 during
startup.

Simon-

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