Subject: Re: large disk preformance (interactive lags in 1.5.1-BETA)
To: None <>
From: Dwight Tuinstra <>
List: current-users
Date: 04/09/2001 12:28:16
Tyrel Beede wrote:
> I recently replaced my 4.5 GB UW SCSI @ 7200 rpm drive with an IDE 30 GB
> @ 5400 rpm.  The switch wasn't optional and I've come to notice that the
> new drive lags with interactive preformance every now and then.  For
> example I'll be running a vi session and things will just kinda bog
> down, it seems to occur at random points( some of the time just after a
> reboot and others after the machine has been up for a few days ).  The
> lag is kinda like working with a vi session over a slow telnet link.
> I'll type on the keyboard and a few seconds later the commands will show
> up.  I've got 96 megs of ram in the machine and I don't even have X
> installed so the machine isn't really being hit hard for memory.  This
> problem isn't really that big because the lag only happens every now and
> then... maybe once a day.  But it never happend on my SCSI drive running
> the same kernel.  Anybody have any tuning ideas?

I've had a similar problem with response lag lately.  The
system is a fresh install from snapshot of 1.5.1-BETA.  The
problem isn't just vi, though.  I sometimes notice it just 
when doing an `ls':

  1) login to several virtual ttys (not even in X, just on console)
  2) start a disk-intensive job running on one or more ttys 
       (eg, untar pkgsrc on one and rebuild kernel on another)
       and let it run for a while.
  3) switch to a free tty and type `ls'.  1-3 second lag.
  4) typing `ls' again immediately gets a quick response.

The disk is an older 5400 rpm IDE model, PIO 4.  There's also
another, even older 5400 rpm drive on the IDE cable, but it's
not even mounted (but I think I saw the behavior even when it
was completely disconnected).  Unfortunately, it'll be at least
a week or two before the HDs are upgraded.

From the behavior, I'd guess its something to do with buffer/
cache behavior not being tuned.  The system I'm seeing this on
has plenty of memory (256Mb) and speed (1Ghz Athlon T-bird on
an IWill KK266 mobo (latest VIA Athlon chipset) ).

If more details are wanted, I can supply them (the machine's at
home, modem not yet working right either, so this is written
from memory while at work).  Let me know what data you'd like.

  --Dwight Tuinstra