Re: hd sometimes 'hangs' a few seconds

["Stephen C. Tweedie" <sct redhat com>]

Hi,

On Mon, Oct 08, 2001 at 10:38:49PM +0200, Hans Schippers wrote:
 
> I recently changed my filesystem to ext3 (from ext2), and since then, my hard 
> disk sometimes seems to 'hang' a few seconds (in fact the whole system hangs 
> then, and only the hd LED is on), before continuing normally... This happens 
> for example (not always though) when I untar an archive and try to ls in the 
> newly created directory...
> 
> Is there an explanation for this? 
> 
> And if so, what's the best solution? 
> (I'm running RH 7.1.94 (roswell))

Which kernel?  You might want to grab a more recent one from rawhide,
as there have been a _ton_ of performance-relevant filesystem and
virtual memory changes in recent 2.4 kernels.

However, it's also worth noting that ext3 is a lot more careful with
your data than ext2.  ext2 trickles data back to disk after a huge
write, but by default ext3 tries to make sure everything starts
getting queued to disk within about 5 seconds of a write starting.
Large archive unpacks could easily result in a lot of instant disk
activity.

There is a looser data writeback mode in ext3: mount with the mount
option "-o data=writeback" to enable it, as described in the mount man
page.  That loses the extra guarantees ext3 gives you about never
seeing stale data blocks on disk after a crash, but you might find
that for interactive use you're happy to make that tradeoff.

Cheers,
 Stephen