Andrew Burgess wrote:

quoted

Basically, B appears to be "write-only"; it will never return an error on a
write, but just try to read from it, and you will be sorry.

It would be interesting to see what SMART says about drive B, especially
the short and long self tests.

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On my hard drives, automatic online testing is turned on, and so is 
automatic offline testing. I run the long self-test once a week.

I have two drives which can play the role of B. One of them has this 
SMART output:

[root@cmccabe-devel root]# smartctl -d ata /dev/sdb -H
smartctl version 5.36 [i686-pc-linux-gnu] Copyright (C) 2002-6 Bruce Allen
Home page is http://smartmontools.sourceforge.net/

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: FAILED!
Drive failure expected in less than 24 hours. SAVE ALL DATA.
Failed Attributes:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE 
UPDATED  WHEN_FAILED RAW_VALUE
   5 Reallocated_Sector_Ct   0x0033   004   004   024    Pre-fail 
Always   FAILING_NOW 133273031255

The other one passes SMART.
Both of them eat data, though.

Colin