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partition size mistakes from Disk Utility partitioning

I'm seeing inconsistent sizes in Disk Utility for partitions of a new
Seagate PATA 750GB disk that I've added to my G4.  I partitioned it
originally a few days ago while running 10.4.9, and I've since then
upgraded to 10.4.11.

I used Disk Utility to partition the new disk to provide partitions
for backups of various partitions on other disks (I use SuperDuper!).
In particular I created three 32GB partitions and then I split the
rest into two equal-size partitions, which at the time showed up as
270GB each.  I had Disk Utility put the default "Mac OS Extended
(Journaled)" filesystems on them.

Later I noticed from the output of 'df' (under xterm/X11) that to my
surprise my two big filesystem were different sizes:

  Filesystem    1M-blocks   Used  Avail Capacity  Mounted on
  /dev/disk1s9     276889     86 276802     0%    /Volumes/Data2
  /dev/disk1s11    340323 230044 110279    68%    /Volumes/clone2_Data3

The Finder confirms the "Avail" figures above, and 'du' confirms
the 'Used' figures.

OK, so I thought I must have made a mistake in the partitioning with
Disk Utility.  No problem, I'll discard the data on that disk and
change the partition sizes.  In fact, I decided to make the smaller
one slightly smaller and the bigger one bigger (because I now had more
total room).  When I started Disk Utility at that point, it showed the
two big partitions as 270.40GB and 332.35GB -- agreeing with the 'df'
output above.  That's a total of 602.75GB, up from the 540GB total I
thought was left for those two according to Disk Utility earlier.

So in Disk Utility/Partition, I drag the dot that's between the two
partitions so that the smaller one gets a little smaller, namely
249.51GB.  Then I check what Disk Utility says the size of the bigger
one is, and it has shrunk even more, to 291.54GB!  The average of
those two new sizes is in fact the 270GB that I tried to make both
their sizes originally.  That's a total of 541GB, compared to the
602.75GB total I had a few seconds before.

I verified that my three other partitions still show up as unchanged
in size (about 32GB each).

I experimented some more and conclude that Disk Utility indeed thinks
it has 541GB to allocate to those last two partitions, no matter what
size I try to make either of them.  If I delete one, the other becomes
541.05GB.


I haven't actually let Disk Utility repartition the 750GB disk yet.
I'm guessing that whatever partitioning I set up in Disk Utility, an
extra 60GB or so will magically show up in the last partition, but I'd
sort of like to know what's going on first.  Note that Disk Utility
says the disk has 698.6GB total, which agrees with the bigger sizing
of the final partition.

Has anyone else observed this phenomenon or know why this discrepancy
occurs in sizes in Disk Utility?  Seems like a blatant bug to me --
much more than a little rounding error.

This is on a dual 1.42GHz G4, with three other internal disks (250GB,
300GB, 300GB).

Martin
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nospam223 (157)
6/2/2008 5:27:02 AM
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