Re: [Bug-ddrescue] ddrescue errors: maybe yes, maybe no

[Adrien Cordonnier]

Hello Antonio,

2014-02-13 19:23 GMT+00:00 Antonio Diaz Diaz <address@hidden>:

BTW, would anybody here find useful that ddrescue could produce compressed logs of rates and reads? I think they may become pretty large (specially the reads log).

I think this is a really good idea. Actually I subscribed to the list last week because ddrescue became really slow, probably because of the size of the log file. 

The disk to rescue is 500 GB with bad sectors mainly at 50% and 75%. I backed up the first 50% then the last 25% with the -r option. I saw that the speed was sometimes 11-15 MB/s, sometimes 5 MB/s in the third quarter. Thus I stupidly ran ddrescue for the third times with a minimum speed of 10 MB/s to get the fast areas first. The speed decreased to around 9 MB/s so I backed up almost nothing more and the log file grew to 7 MB. Now, ddrescue speed has decreased to 10 kB/s, 1000 times less than dd at the same position.

I think it would be good to have the option to keep the previous versions of the log file. Hence I suggest the option --history with the following behaviour:

1) read the log file e.g. "logfilename", if "logfilename" is an archive, read the last log file by default.

2) append it in "logfilename.7z", in the archive rename the log file with the date when the log file was created (in ISO format)

3) create the new log file as "logfilename" or if "logfilename" is an archive, append the new log file to the archive with the date of the current command.

I suggest 7zip compression because it gives much better compression. For example my 7 MB log file (available if you want) is between 300 kB and 500 kB with zip, gzip or bzip2 but only 84 kB with 7zip (with default fileroller parameters).

I am interested by any idea that you may have to proceed with the back up of my disk. Currently, I consider either:

a) to run dd on 0-50%, 55-70% and 75-100%, and ask ddrescue to finish the work by guessing what the log file should be.

b) to write a python script to simplify my 7 MB log file by replacing all 3 lines non-tried/1 good sector/non tried with a long non-tried area.

Cheers,

Adrien