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Message-ID: <8704040310.AA08252@ucbvax.Berkeley.EDU>
Date: Fri, 3-Apr-87 15:25:00 EST
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Posted: Fri Apr  3 15:25:00 1987
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> Date:     Thu, 2 Apr 87 15:06 EST
> From:     <SIBLOCK%MCMASTER.BITNET@wiscvm.wisc.edu>
> Subject:  SHOW QUOTA vs. DIR/SIZ/TOT [...]
>
> We've recently had to do a system-wide purge of old files to release some
> space on one of our RA81 user disks.  Someone brought to my attention that
> when he does a $dir/siz/total [...] from his root directory, the total blocks
> shown are 2,000 blocks less than $show quota displays.  Now, I've always
> noticed a slight difference between the two outputs, but 2,000 blocks on a
> 5,000 block total disk usage?   Will this affect what I see as free space
> from a $show device d command?  Who's correct, $dir or $show quota?

Disk quota should be equal to the sum of the following:

1.  Sum of disk allocation for the extents for all files owned by the user.

    Note that DIR/SIZE=ALLOCATED is the correct way to determine the disk
    allocation for the extents of a file.

    Also note that $DIR/SIZE/TOTAL [...] does not include the allocation
    charged for [000000]username.DIR, or any files owned by the user but
    stored in a different root.

2.  Sum of disk allocation for the headers for all files owned by the user.

    There is at least one file header for each file, and a file header costs
    one block.   Files that are extended regularly are particularly likely to
    have multiple file headers.  A file may also have multiple file headers
    if free space is so fragmented on the disk that the file could not be
    allocated in one place.

The disk quota value can be inaccurate if disk quota checking was turned off
for a time by the system manager, and then turned back on.  It can also be
inaccurate if the system crashes or the disk is put offline while the disk is
mounted, and the system manager does not MOUNT/REBUILD the disk or use the
DISKQUOTA REBUILD command to recalculate disk quotas.  This is because
changes in disk quota and usage are cached in memory, which is lost when the
system crashes.

So, have your user type the following command:

  $ DIR/SIZE=ALL/GRAND [...],[000000]username.DIR;1

Assuming a well-structured and ``clean'' disk volume, the output from SHOW
QUOTA should match the sum of the allocation and the number of files reported
by DIRECTORY very closely.

Ed McGuire
Grinnell College
MCGUIRE@GRIN2.BITNET