Re: Mysterious disk activity
On Mon, Jan 27, 2003 at 10:03:05AM +0100, Rogier Wolff wrote:
> On Sun, Jan 26, 2003 at 01:58:04AM +0000, Pigeon wrote:
> > Hi,
> >
> > I get these occasional very long bursts of disk activity, usually but
> > not always within an hour or so of booting up, during which the HD LED is
> > on continuously and the machine is very slow to respond. There were
> > cron jobs running global finds, which I knocked out; this helped, but
>
> Yes, that's for the locate command. You can use "locate filename", and
> it will quickly (i.e. within two seconds, if you have less than a couple
> of million files unlike us....) show you where files live that have
> that name.
AARGH! And there was me using 'find dir -name x' and hoping 'dir'
didn't have to be /...
> > didn't stop it entirely. To make it more mysterious, ps ax during such
> > a burst shows nothing untoward:
>
> If the "knock them out" is by hand, then you will have let "find" run
> for a couple of seconds. A little later, your system will decide that
> "find" accessed a bunch of directories, and will write hte "last access"
> time on those directories back to disk. That would explain the disk IO
> burst.
AH. That probably DOES explain it, and why nothing shows up in ps ax
at the time. Thanks!
> Note that "load" does not always correspond to CPU usage: The system
> will count processes waiting for disk IO towards the load as well.
> This represents the "slowness" that lots of disk IO causes you to
> feel.
Yeah. That's why a nice SCSI drive is the next thing on my
get-this-hardware list!
> The updatedb (that find running for locate) will run from the dayly
> cron jobs. There might be a bunch of other things that are considered
> useful to run every day.
>
> Oh, most systems (I haven't checked debian) will move the "dayly" jobs
> to the middle of the night if you leave your system running....
No, I switch it off when I'm not using it. I sleep in the same room
and 4 fans and 6 disk drives make a lot of noise... Also the power
consumption, and resulting temperature rise in the room, are
non-negligible.
Pigeon
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