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From: peterson@UTAH-CS.ARPA.UUCP
Newsgroups: mod.computers.apollo
Subject: Re: Apollo disk space erosion
Message-ID: <8702051810.AA04259@utah-cs.ARPA>
Date: Thu, 5-Feb-87 13:10:26 EST
Article-I.D.: utah-cs.8702051810.AA04259
Posted: Thu Feb  5 13:10:26 1987
Date-Received: Sat, 7-Feb-87 15:38:16 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 22
Approved: apollo@yale-comix.arpa

Unlike native Unix boxes, Apollos do not have an explicit swap area.
Instead, user paging space is allocated from the general pool of free
disk space.

If a diskless node crashes or a process dies abnormally (e.g, "sigp -blast"
or vanishes with a "process not found") space used by the process may
not be reclaimed.  The result is that over a period of weeks disk space
leaks away.

The best way to reclaim this space is to take the node down and run
SALVOL. There is another program, find_orphans, that tracks down objects
that are allocated on the disk but don't have a directory entry (these
can also result from crashes or abnormal process terminations).
However, only run find_orphans when there is no activity on the disk.
Otherwise, it might decide a file is an orphan if it finds it while it's
being created...)

There is a major advantage to this way of allocating swap space - it makes
adding or removing diskless partners a fairly trivial process.  (If you've
ever watched a Sun adminstrator reformat a disk all night to build new swap
partitions you'll know what I mean.  I think Sun is switching to the global
paging pool scheme in their next release...)