Version 1.11 of GNU ddrescue released

[Antonio Diaz Diaz-2]

I am pleased to announce the release of GNU ddrescue 1.11.

GNU ddrescue is a data recovery tool.

The homepage is at http://www.gnu.org/software/ddrescue/ddrescue.html.

The sources can be downloaded from http://ftp.gnu.org/gnu/ddrescue/ or
from your favorite GNU mirror.

This version is also available in lzip format. If your distro doesn't
yet distribute the lzip program, you can download it from
http://www.nongnu.org/lzip/lzip.html

The md5sums are:
7146046bb1851351d1337bb1f5b4e903  ddrescue-1.11.tar.gz
af840dd177e968493e2fcef1fb19d719  ddrescue-1.11.tar.lz

This release is also GPG signed. You can download the signature by
appending ".sig" to the URL.

Changes in version 1.11:

   * In case of error writing the logfile to disc, the user is now given
the possibility of fixing the problem and continue.

   * The splitting algorithm has been modified to read secuentially the
areas smaller than a threshold size.

   * After every read error, ddrescue now verifies the input file has
not disappeared.

   * In rescue mode, ddrescue now shows the time elapsed from the last
successful read.

   * Signals SIGUSR1 and SIGUSR2 are now ignored by ddrescue.

   * Descriptions of "--direct", "--synchronous" and "--sparse" in the
manual have been made clearer.

   * Description of rescue algorithm in the manual has been made clearer.

   * "make check" now verifies that files are open in binary mode.

   * A warning about logfile usage has been added to "ddrescue --help"
output.


Please send bug reports and suggestions to bug-ddrescue@...


Regards,
Antonio Diaz, GNU ddrescue author and maintainer.



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[Antonio Diaz Diaz-2]

John wrote:
> What's the difference between ddrescue and dd_rescue? Or are they the
> same thing? Seems to be synonymous on the web.

GNU ddrescue and dd_rescue are very different programs. The confusion
comes from some distros distributing dd_rescue in a package named ddrescue.

See these descriptions from John Gilmore
http://www.toad.com/gnu/sysadmin/index.html#ddrescue

"Kurt Garloff's dd_rescue was the first attempt to improve on this [dd].
It reads and copies bigger blocks until it sees an error, then slows
down and goes back, and reads single sectors. After a while it speeds up
again. It can also read backward, and can quit after it gets some
specified number of errors. It keeps a 3-line display updated in your
text window so you can see what it's doing. If you run it simply, it
just does what "dd bs=64k" does until it sees an error, then backs up
and does "dd bs=512". If it gets an error reading a sector, it doesn't
write to that sector of the output file, but it skips past it to write
the next good one, so everything stays in sync. It seeks the input and
output in parallel so it makes an exact copy of the parts that it can read.

LAB Valentin's dd_rhelp. is a complex shell script that runs dd_rescue
many times, trying to be strategic about copying the drive. It copies
forward until it gets errors, then jumps forward by a big jump looking
for either the end of the drive, or more easy-to-read stuff. Once it
finds the end of the drive, then it starts working backward, trying to
close up the "hole" that it hasn't read yet. As it encounters errors, it
skips around looking for more error-free parts of the drive. It only
reads each sector once. It reads the logfile output of dd_rescue to see
what happened and to figure out what to do next.

One problem with dd_rhelp is that it's a shell script, so it's really
slow and consumes massive resources. On one of my drives that had about
2900 bad sectors on it, dd_rhelp would waste upwards of 15 minutes
deciding what blocks to tell dd_rescue to try reading next. During that
time it makes about 100 new Unix processes every second.

Antonio Diaz Diaz's GNU ddrescue learned from these experiences. It
combines both dd_rescue's ability to read big blocks and then shift
gears, with dd_rhelp's ability to remember what parts of the disk have
been looked at already. It keeps this info in a really simple logfile
format, and keeps it updated every 30 seconds, or whenever it stops or
is interrupted. It's written in C++ and it's small and fast.

It starts off running like "dd", blasting through large error-free
areas. When it gets an error, it writes out any partial data that it
received during that read, and KEEPS GOING to the next big block. It
notes in the logfile that a bunch of sectors (the first erroneous one,
plus whatever ones followed it in the multi-sector read) were skipped.
And keeps going. So it reads through the entire disk in big blocks
first. Then it goes back to "split" the skipped parts, trying to read
each sector individually. The compact logfile always shows which chunks
of disk have been read OK, have been read with errors, have been read
one sector at a time with errors, or have never been read yet."


Regards,
Antonio.


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