[RndTbl] Open Source Backup/cloning to USB HDD

Adam Thompson athompso at athompso.net
Tue Oct 27 21:38:19 CDT 2009

On Tue, Oct 27, 2009 at 19:18, Adam Thompson <athompso at athompso.net> wrote:
> All modern drives (IDE, SATA, SCSI & SAS, anyway) reserve an entire track
> (or more) for bad-sector remapping.  The firmware automatically remaps any
> sector that requires more than X number of retries to read or write
> successfully.  This is done transparently to the user, operating system,
> ATAPI controller, etc. - it's handled 100% internally.

Updating my own information, it seems that many drives only attempt to
reallocate bad sectors on WRITE, and *not* on read.  The *destructive* SMART
"Long" test causes every sector to be re-written, which will accomplish this
goal, but at the cost of losing all your data.

Windows' ScanDisk program (or CHKDSK, under some versions of Windows) can do
a non-destructive surface scan that only tests READS.

Gibson Research (GRC)'s SpinRite (http://www.grc.com/spinrite.htm) is the
only program that I know and would recommend, that I know can do
NON-destructive full-disk read-write testing.  It has several limitations,
including its US$90 price, but Steve Gibson "wrote the book" on HDD testing
and it shows.  FYI, if you think $90 is too much money, consider that Steve
(the author) only writes in one programming language - x86 assembly!

Reportedly, some vendor diagnostics can do non-destructive write testing,
but the current versions of Seagate SeaTools and WD DataLifeguard do not
appear to have this functionality, and Fujitsu, HGST, Toshiba, and Samsung
don't produce drive test utilities [any more].

It would be fairly simple to implement something that does this in Linux
with a shell script, something that looped over X megabytes of space,
dd(1)'d 1MB of data at a time to a temporary file, dd(1)'d it right back to
the drive at offset X.  The implementation is left as an exercise for the
reader :-).

-Adam Thompson
<athompso at athompso.net>
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