硬碟故障救星 - ddrescue

眾所周知硬碟是有壽命的，作為電腦用家，一定曾經歷過硬碟在讀取資料途中，發出怪聲後卡住無法繼續讀取的情形。這時今次介紹的ddrescue說不定可以幫上忙。


硬碟在讀取途中發出怪聲後卡住，是因為遇上壞掉的部分時，系統會一直繼續重試，以致卡住無法取得數據。ddrescue的前提則是優先救出所有健全 的數據， 它會跳過壞掉的部分，繼續讀取餘下的數據。取得所有健全數據後，才回頭到剛才跳過的部分重試，並取出健全的數據。

以上兩個步驟都無法讀取的部分，將以磁區 為單位分割後再重試。ddrescue雖是一個只可在Linux下運作的工具，但支援包括NTFS在內的大部分檔案系統，是救出Windows數據時的其中一個選擇。


Forensic wiki:

ddrescue is a raw disk imaging tool that "copies data from one file or block device to another, trying hard to rescue data in case of read errors." The application is developed as part of the GNU project and has written with UNIX/Linux in mind.

ddrescue and dd_rescue are completely different programs which share no development between them. The two projects are not related in any way except that they both attempt to enhance the standard dd tool and coincidentally chose similar names for their new programs.

From the ddrescue info pages:

GNU ddrescue is a data recovery tool. It copies data from one file or block device (hard disc, cdrom, etc) to another, trying hard to rescue data in case of read errors.

Ddrescue does not truncate the output file if not asked to. So, every time you run it on the same output file, it tries to fill in the gaps.

The basic operation of ddrescue is fully automatic. That is, you don't have to wait for an error, stop the program, read the log, run it in reverse mode, etc.

If you use the logfile feature of ddrescue, the data is rescued very efficiently (only the needed blocks are read). Also you can interrupt the rescue at any time and resume it later at the same point.

Automatic merging of backups: If you have two or more damaged copies of a file, cdrom, etc, and run ddrescue on all of them, one at a time, with the same output file, you will probably obtain a complete and error-free file. This is so because the probability of having damaged areas at the same places on different input files is very low. Using the logfile, only the needed blocks are read from the second and successive copies.

轉自 
http://www.forensicswiki.org/wiki/Ddrescue
http://www.linuxpilot.com/software/kiji/2010080701