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Date:      Sun, 17 Feb 2002 17:05:48 +0100 (MET)
From:      Thomas Schuerger <schuerge@wjpserver.CS.Uni-SB.DE>
To:        freebsd-fs@freebsd.org
Subject:   New dir layout slow on full disks!?
Message-ID:  <200202171605.g1HG5ml26850@wjpserver.cs.uni-sb.de>

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Hi!

I'm using 4.5-RELEASE and am quite happy with the new directory layout
stuff. It really speeds up file scans etc. a lot.

But there can be serious performance loss:

When a disk is nearly full (e.g. 98%, but still 1,6 GB free, values
taken from "df"), creating files becomes very slow. I noticed this
when I wanted to install a big port (e.g. kdebase2). The extraction of
the .tar.gz archive took really long and made my system more or less
unusable. tar took something like 90-99% system time for 3 minutes.

I compared extracting the same archive in /tmp (slice 1,disk 1, 3%
full) with tar compared to extracting it somewhere in /usr/ports/...
(slice 2,disk 1, 98% full). The latter took 8 times as long and almost
completely blocked my system (note that this is on the same disk but
on a different slice). Both slices use soft-updates.

It seems that looking for free nearby blocks in the new directory
layout algorithms is really slow when there are few free blocks
available.

Is anyone else experiencing this?


Greetings,
Thomas.

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