Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!ames!amdcad!amd!intelca!mipos3!omepd!perry
From: perry@omepd.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: Lost clusters, chains, and files
Message-ID: <781@omepd>
Date: Wed, 10-Jun-87 15:03:23 EDT
Article-I.D.: omepd.781
Posted: Wed Jun 10 15:03:23 1987
Date-Received: Sat, 13-Jun-87 08:15:17 EDT
References: <1855@isis.UUCP>
Sender: news@omepd
Reply-To: perry@inteloa.intel.com (Perry The Cynic)
Organization: Intel Corp., Hillsboro
Lines: 34
Summary: What's a lost cluster...

In article <1855@isis.UUCP> tkoppel@isis.UUCP (Ted Koppel) writes:
>Earlier this evening, when running a "chkdsk b:*.*", I got the
>wonderful and mysterious message:
>   1 lost cluster found in 1 chain -- 
>    Convert lost chains to files?
>
>What does this mean? The chkdsk went on to say that the disk itself
>had all sorts of file system errors .. Can one recover from this 
>"lost cluster condition" without reformatting the disk?

A *cluster* is the logical storage unit on a disk; it is one or more disk
blocks (512bytes each). A *lost cluster* is a cluster that is marked *used*
(i.e., is not free space) but that does NOT belong to any file (or directory)
on the disk. That shouldn't happen but sometimes it does, especially when your
machine crashes during a write operation.
Clusters are *chained* on your disk (in the FAT, to be exact), with a
directory entry pointing to the first block. Thus, if the directory entry gets
trashed all clusters in that *chain* become lost.
CHKDSK gives you the option to recover these *lost clusters*. Call
	CHKDSK /F
(for FIX it) and answer YES to the question above. CHKDSK will create files
FILEnnnn.CHK in the root directory of the disk that contain the lost clusters,
one for each chain. You can then examine these files with an editor or dumper
or whatever, and use them as usual (or delete them to free the space). This
does NOT destroy anything on your disk (the damage has already been done :-)
and doesn't touch files that have no problems. See your DOS manual (CHKDSK
command) for details.
Oh, one thing that probably confused you: if you call CHKDSK *without* the
"/F" argument, it still asks you the conversion question, just to tell you
then that it didn't do anything. Can't make it too clear here now, can we?
------------------------------------------------------------------------
  <<  Perry The Cynic >>		   =>> perry@inteloa.intel.com <<=
				      ...!tektronix!ogcvax!omepd!inteloa!perry
   (Peter Kiehtreiber)				...!verdix!omepd!inteloa!perry