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Date:      Sat, 3 Apr 1999 02:48:22 +0200 (CEST)
From:      oliver.fromme@heim3.tu-clausthal.de
To:        FreeBSD-gnats-submit@freebsd.org
Subject:   kern/10927: Bug in UFS/FFS: time / space optimization on large partitions
Message-ID:  <199904030048.CAA51150@pegasus.rz.tu-clausthal.de>

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>Number:         10927
>Category:       kern
>Synopsis:       Bug in UFS/FFS: time / space optimization on large partitions
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Apr  2 16:50:01 PST 1999
>Closed-Date:
>Last-Modified:
>Originator:     Oliver Fromme
>Release:        FreeBSD 3.1-19990318-STABLE i386
>Organization:
Clausthal University of Technology
>Environment:

FreeBSD pegasus.rz.tu-clausthal.de 3.1-19990318-STABLE
FreeBSD 3.1-19990318-STABLE #0: Wed Mar 24 19:19:25 CET 1999
inof@pegasus.rz.tu-clausthal.de:/usr/src/sys/compile/PEGASUS
i386

>Description:

We're running a Squid proxy/cache on three large disks (9 Gb
each).  Squid uses them evenly, so all of them have about the
same amount of used space.  Recently we got these kernel
messages:

Apr  1 13:10:53 pegasus /kernel: /var/cache2: optimization changed from TIME to SPACE
Apr  1 14:00:58 pegasus /kernel: /var/cache1: optimization changed from TIME to SPACE
Apr  1 14:30:21 pegasus /kernel: /var/cache3: optimization changed from TIME to SPACE

At that time, the disks were about 35% used.  Unfortunately
I don't have a "df" output from that time for the exact
numbers.  Right now (36 hours later), it looks like this:

Filesystem  1K-blocks     Used    Avail Capacity iused   ifree  %iused  Mounted on
/dev/da1d     8688136  3182309  4810777    40%  208665 1965797    10%   /var/cache1
/dev/da2d     8688136  3180420  4812666    40%  211075 1963387    10%   /var/cache2
/dev/da3d     8688136  3180014  4813072    40%  209630 1964832    10%   /var/cache3

The partitions were _never_ more filled than this.  The amount
of used space has been continually increasing (from 0% to 40%)
since the machine was installed about 10 days ago.  There is
no reason to switch optimization from time to space.
And, in fact, it's rather annoying because the Proxy is quite
busy, and having the FS optimizing for time would be a valuable
advantage.

I suspect that there must be a bug in the 64bit calulations of
the UFS/FFS implementation which decides about the type of
optimization.  Note that the partitions are > 2^31 bytes.

>How-To-Repeat:

Create a large filesystem (> 8 Gb) and start filling it until
about 35%.

>Fix:
	
None known.  :-(


>Release-Note:
>Audit-Trail:
>Unformatted:


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