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From: jb10320@UXA.CSO.UIUC.EDU (Jawaid Bazyar)
Newsgroups: comp.sys.apple
Subject: What to do about a bad block
Message-ID: <8904140247.AA09689@uxa.cso.uiuc.edu>
Date: 14 Apr 89 02:47:44 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 44

/* Written  3:07 am  Apr 13, 1989 by TMPLee@DOCKMASTER.NCSC.MIL in uxa.cso.uiuc.edu:info-apple */
/* ---------- "What to do about a bad block" ---------- */
From: TMPLee@DOCKMASTER.NCSC.MIL

] I recently got a ProDos "DISK I/O" error when downloading a file with
] kermit.  The file looks like it got saved OK.  (I can read it all and it
] all seems to be there.)  Just to be safe I decided to run the Finder's
] "verify volume" on my harddrive.  It told me that only one block,
] #16384, was bad.  (The drive is a 40Meg Everex set up as a 32Meg volume
] under P16 but I'm now running GS/OS -- I haven't had the courage to dump
] the whole thing and reformat/partition it to use all 40M) Soooooo, four
] questions --

] a) is there any easy way of finding out what file and/or directory 16384
] is in, or if it might in fact be unused?  (note that 16384 = 2**14,
] which seems an interesting coincidence.)

     No, not really.  It mainly consists of using a program such as Bag of
Tricks II to scan all the files on the disk to find the one that containts
the bad block (if any).  Note that B**4 (described below) does NOT find
bad files for you. It is asssumed that you learned of the bad block by trying
to access a file which ProDOS promptly gave you an I/O error for.

] b) if it is unused, or even if not, how does one go about marking it as
] a bad block?

    Just have ProDOS pretend that it belongs to a file. This is what my
utility, Big Bad Block Buncher (or B**4) does. BTW I just sent this program
to APPLE2-L and COMP.BINARIES.APPLE2.

] d) does ProDos do a read-after-write to verify that what it writes
] actually gets written correctly?
  
    Yes, but that really only does you any good if it wrote correctly in the
first place. If it doesn't verify, it'll just go "blork" and give you an
I/O Error.

] TMPLee@Dockmaster.ncsc.mil

jawaid bazyar				"The only way to do it is to go into
jb10320@uxa.cso.uiuc.edu		 the future and assume that it has
					 already been done. Then go back in
					 time and it should be done, Wilbur."
					    Mister Ed on LSD