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Re: [Bug-ddrescue] Perl script to modify ddrescue log files

From: Burkart Lingner
Subject: Re: [Bug-ddrescue] Perl script to modify ddrescue log files
Date: Wed, 26 Oct 2011 23:34:06 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20110922 Thunderbird/3.1.15

Hi Antonio!

I am no filesystem expert, but no filesystem seems to be using a block
size smaller than 1024 bytes. So using 512 as a default for ddrescuelog
does not seem to be useful.

FAT comes to mind, but besides floppy disks which are ancient enough it's probably only found using 512-byte sectors on really old hard disks. So yes, if ddrescuelog is primarily meant to output a list of damaged file system blocks then 512 byte would be a seldomly used default. However, I used to think of ddrescuelog as a more low-level tool, i.e. working on the same (hard disk block) level as ddrescue. For instance I use it to generate lists of bad sectors (512 byte) without any regard for higher-level structures like file systems.

As I said before I don't really care all too much about the default value. Not to mention people may already have written scripts with the old 4 KiB default that would stop working if the default was changed now.

One more thing to take care of, though: Imagine you first use ddrescue and there is one bad block (512 byte) surrounded by successfully read data. Using ddrescuelog's new --change-types option to i.e. invert the block types together with a default 4 KiB block size, would that turn the 3.5 KiB surrounding the bad block into the same block type as the bad block? Or vice versa? Or are block boundaries and thus block sizes completely ignored by --change-types?

Bye, Burkart

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