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From: kelvin@thed (Kelvin Hill)
Newsgroups: comp.sys.acorn
Subject: TAR & Disk Corruption.
Summary: TAR corrupts hard disks?
Keywords: Aaaarrrggghhhh!!
Message-ID: <kelvin.677235945@thed>
Date: 18 Jun 91 09:05:45 GMT
Sender: @mips2.ma30.bull.com
Organization: Bull HN Informations Systems Inc.
Lines: 54

Some time ago, a somewhat irate user reported that he had been using tar
to backup or restore some files from/to a hard disk, and that as a result
had had his root directory partially wiped. At the time, I thought 'pilot
error'and put it to the back of my mind.
I have now to reconsider this situation after a similar nightmare hit me 
yesterday. This serves as both a warning and a request for advice. Let me
tell the (nearly) whole story.
Yesterday, I got a bit twitchy about not having backed up the 2 * 40Mb
ST506 drives in my 440/1+Arm3 system. So, I pre-formatted 120 floppies
to take the backups onto. As I have a 15Mb MS-DOS partition on each disk
I wanted to use tar to perform the backup, instead of the other method of
file by file copy. This is because the file by file methods won't save the
DOS areas.
I used the version of tar that comes with the !Extract/!Submit software
from comp.binaries.acorn, so it's fairly up to date. I also loaded the
FS_VARS module that tar seemed to require at one time. As far as I know
it may still do so.
I copied tar to a 256kb ram disk and made it my current directory. I then
fired tar up with the following command line.
             tar -cvBf 10 adfs::1.$.Backup4 adfs::4.$
(The B and 10 are to use 5120 byte blocking. I *think* it's B not b.)
The first 3 floppies were saved to correctly and all looked wonderfull, BUT
halfway through the 4th floppy, the system crashed. Not just tar, but the 
whole system just fell over. The screen cleared and the hard disk light came
on solid. 
I did a ctrl-(reset button) to bring it back up and this is where the panic
set in. The hard disk adfs::4 was now badly corrupted and giving errors.
I now had 4 randomly located 'broken directories'. Of these, 2 were at root
level and 2 were subdirectories. I also had at least one damaged data file.
I suspect that there may well be more data file damage but it takes a long
time to check out 40Mb of individual files.
To cut the story short, I have recovered most of the broken directories, 
reformatted and rebuilt both hard drives and tested some of the data files
on the corrupted disk. There is still a lot of checking to do though.

Summary.
-------

Tar has now been implicated twice in the corruption of hard disks during 
'normal' operation. While this may be co-incidence, should we be using 
this product to distribute software in comp.binaries.acorn? I for one
dont trust it any more! 
Thats the warning bit over with...  now for the request for advice...
What do people consider to be the best method of backing up my two hard
disks, considering the problem of the 15Mb DOS partitions? A SCSI tape
would be nice, but then so would the money to buy it! I have at the moment
to probably stick to diskettes. Any suggestions would be appreciated.

Kelvin.

--
Kelvin J. Hill - BULL HN Information System Ltd, Hounslow, England, UK.
Internet - kelvin@thed.uk22.bull.com   | UUCP - kelvin@cix.compulink.co.uk
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