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- Path: sparky!uunet!ogicse!uwm.edu!wupost!think.com!ephraim
- From: ephraim@think.com (Ephraim Vishniac)
- Newsgroups: comp.sys.mac.system
- Subject: Re: "Get Info" reports different size when file is moved
- Message-ID: <1592g8INNptm@early-bird.think.com>
- Date: 30 Jul 92 15:39:52 GMT
- Article-I.D.: early-bi.1592g8INNptm
- References: <1992Jul30.141956.13014@eplrx7.es.duPont.com>
- Distribution: usa
- Organization: Thinking Machines Corporation, Cambridge MA, USA
- Lines: 41
- NNTP-Posting-Host: leander.think.com
-
- In article <1992Jul30.141956.13014@eplrx7.es.duPont.com> poster writes:
- >The specific situation.
- >----------------------
- >Mac with system 7 is used to create an MS-Word file (with one word in it).
- >Get Info reports file is: 3K (2048 bytes used)
-
- >Document is transferred to floppy.
- >Get Info reports this copy is: 2K (2048 bytes used)
-
- >Floppy put into system 6 Mac, Get Info shows same as previous (2K)
-
- >Document copied to system 6 Mac's hard drive (a large drive ~1.2GB)
-
- >Get Info reports this copy is: 17K (2048 bytes used)
- >----------------------
- >Why would 17K of disk space be needed to store a 2K document. I know there is
- >some overhead with format info, directory info and pointers, but
- >a 17:2 ratio? Would sectors on a large capacity drive be much larger (some
- >minimum greater than 2K)? Or does it relate to a difference in the way system
- >6 and system 7 handle these things?
-
- Disk space is allocated in "volume allocation units," which aren't
- necessarily sectors. The Mac keeps track of which VAUs are allocated
- in a bitmap for each volume. The bitmap has a fixed size, which means
- that your 1.2GB disk, with about 2,400,000 sectors, doesn't have very
- many more VAUs than your 800K floppy, with 1600 sectors.
-
- So, what you're seeing is that the big disk's VAU is 34 sectors (17K).
- You simply can't allocate any less space than that for a non-empty
- file. If this is a significant problem, partition your disk. The
- smaller volumes will have smaller VAUs.
-
- This is unrelated to System 7/6 differences. The volume organization
- is unchanged since the introduction of HFS around System 4.1(?). Of
- course, nobody had a 1.2GB disk on their Mac then.
-
- --
- Ephraim Vishniac ephraim@think.com ThinkingCorp@applelink.apple.com
- Thinking Machines Corporation / 245 First Street / Cambridge, MA 02142
- One of the flaws in the anarchic bopper society was
- the ease with which such crazed rumors could spread.
-