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From: mjn@sbcs.sunysb.edu (The Sixth Replicant)
Newsgroups: comp.os.aos
Subject: Re: How to find *real* file sizes in AOS/VS...?
Message-ID: <3536@sbcs.sunysb.edu>
Date: 22 Sep 89 14:58:01 GMT
References: <1702@murdu.oz> <116@harald.UUCP> <8416@boring.cwi.nl>
Sender: news@sbcs.sunysb.edu
Reply-To: mjn@sbstaff2.UUCP (The Sixth Replicant)
Organization: Tyrell Corp.
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In article <8416@boring.cwi.nl> dik@cwi.nl (Dik T. Winter) writes:
>About getting the disk space used by a specific file.
>
>I would think that a dumped file might use more space than a file that is
>not dumped!  The previous poster alluded to compression techniques where
>large blocks of 0's were not written to disk.  They might very well expand
>when dumping in AOS (I do not know).

In point of fact, DUMP, DUMP_II and, I believe MOVE, do zero elimination.
Whenever there are blocks of zeros, these are not written to the output. 
There is a system call which has an option to give the next _allocated_
block. I believe it's ?BLKIO, but its been several years. This is used
by DUMP_II to avoid spending large quantities of CPU time while scanning
zeros from large, unallocated files.

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Marc Neuberger                                      mjn@sbcs.sunysb.edu



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Marc Neuberger                                            mjn@sbcs.sunysb.edu