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From: thompson@PAN.SSEC.HONEYWELL.COM (John Thompson)
Newsgroups: comp.sys.apollo
Subject: re: SR10.3 file system changes ?
Message-ID: <9106051318.AA01565@pan.ssec.honeywell.com>
Date: 5 Jun 91 13:18:39 GMT
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> Recently I copied a directory on a SR10.2 DNXXX system to
> an SR10.3 HP400 system.  The directory on the SR10.2 was
> about 60 M in size, but when I did a "du" on the HP400 it
> gave a size of about 104 Mbytes.  
> 
> If I check with "df" on the HP400 after the copy, I can see
> that about 70M has been added to the disk in stead of the expected
> 60M.
> 
> I suppose HP changed the block sizes of the file system ?
> So the final and strange question is : how much disk space has been 
> allocated ?  104M, 70M or 60M.

None of the above.  The real answer is "42."    :-)
(See Hitchhikers Guide To The Galaxy if you're confused)

Seriously, there were some changes, and there are other reasons your
disk space could show up weird.
1) At 10.3, the disk block size went from 1K to 4K (except on the DN10K, which
   always used a 4K block size).  This means that a 1 byte file will take up 
   4K bytes on a 10.3 formatted disk, and 1K byte on a 10.[012] formatted disk.
   If you have a lot of tiny files, this can give you a 4X increase in disk
   usage.  We noticed about a 10% increase in our average, which is what 
   HP/Apollo said to expect, too.  (I can't remember where I read about this,
   but I remember reading about it....)
2) All of the disk-usage routines give "bad" results when you have hard-links.
   The routines don't bother checking whether an object has been counted once,
   so they count its space for every entry in the listing.  We are using up
   740MB of our 440MB disk, and it still has 45MB free!
3) The Unix 'ls' command gives the total space of a sparse object, not just
   the allocated part.  This may cause some "Huh?" as well.  (In fairness, 
   Aegis lists the total space too, but they also list the blocks used, which
   is a more reliable indicator of actual usage.

-- jt --
John Thompson
Honeywell, SSEC
Plymouth, MN  55441
thompson@pan.ssec.honeywell.com

When in danger, when in doubt --
run in circles, scream and shout.