UNIX 4.2 thrashing - the cause?

[preece at ccvaxa.UUCP]

>	I believe there is a lesson here.  4.2bsd sites should try to keep all
>	filesystems below 90% full (especially those where a great amount of
>	creation and deletion take place daily - /usr, /usr/spool) or suffer
>	degradation.
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You don't really have to try very hard to keep your filesystems under 90%
full -- 4.2 will keep normal users from pushing them past that point.
You're missing the fact that the df listing is giving you percentages
relative to a 90% ceiling, NOT relative to total capacity.  Note that
a filesystem shown as 100% full and with 0 blocks available will still
have 10% fewer blocks in the used column than in the capacity column.
Superusers are able to go beyond the 90% limit and df will obediently
report that up to 110% of the filesystem is being used.

Still, it's probably better to try to keep from pushing the 90% (shown
as 100%) level.

scott preece
ihnp4!uiucdcs!ccvaxa!preece