disk space : USED+FREE=TOTAL?

[Thomas Omerzu]

In article <2697.26d4fadc at csc.anu.oz> axt654 at csc.anu.oz writes:

>Hi,
>	I've got a DECStation 3100 running Ultrix 2.1. We have a 600Mb hard disk
>with three partitions. Why doesn't USED+FREE=TOTAL ? I assume it isn't swap
>space as that's a separate partition (isn't it?) so maybe it's because the disk
>is fragmented? If so, how do you pack a ultrix disk? It seems we're missing
>over 50Mb!

Maybe you should have a glance at the man page for the `newfs' command:

[...]
     -m free space %
               The percentage of space reserved from normal
               users; the minimum free space threshold.  The
               default value used is 10%.
[...]


So, that place is not missing, it's just reserved.
`Normal' users are prevented from writing when disk capacity
reaches 100%.
The remaining space con only be used by processes running under
uid root.
This feature ensures that system processes will not be blocked
by users who consumpt all available disk space.

You may change the default value of 10% reserved space via the -m option
of newfs while creating a filesystem.
But you should be careful about this; at least all filesystems
that are frequently used by system processes (/, /usr)
- especially if that filesystem is also writable by ordinary
users (like /usr/tmp on the /usr filesystem) - 
should have a reasonable amount of reserved space.


Bye,
	Thomas.



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