DrDD- DataRescue's DD freeware

DataRescue's DD (in short DrDD) - is a graphical disk imager intended for data recovery and backup of partially corrupted storage devices. DrDD creates complete or partial images of disks or memory cards to files on another storage device, allowing multiple data recovery attempts on the raw data, thereby minimizing the risk of damaging the corrupted media further. DrDD is available for Windows PC and Mac OS X machines.

Source: this is the damaged storage device you want to recover from, in this case, as 750 GB NTFS drive.

Data Rescue 3

Data Rescue 3 is a program that every Mac user should at least know about, if not own outright, for those times when you need to restore important files. Download the latest demo version of PhotoRescue Wizard ZIP / DMG File (3.4.0.13436 - Feb 23, 2014) this version will work on Mac OS X 10.2 and above (including Lion). It is optimized for both Intel and PowerPC Mac. The demo version will show you an accurate preview of the recoverable pictures and will allow you to take card backups. Many free data recovery programs exist that can help recover your accidentally deleted files. These file recovery programs can help you recover, or 'undelete' files on your computer. Files you have deleted are often still present on your hard drive (or USB drive, media card, smartphone, etc.) and can be recovered using free data recovery software. Data Rescue III is an application for Mac that can be useful to recover an entire hard drive or only the files that you indicate. It supports practically all file formats. However, to run Data Rescue II, it is necessary to have either another hard drive or an external drive that will be used to store recovered files. It is recommended that you download the Data Rescue 3 demo from our website to scan your network drive (which must be connected via FireWire or USB) to see if Data Rescue can see the files on it. Data Rescue 3 External Drive Recovery is only available on the Mac App Store. Requirements: OS X 10.6.6 - 10.7 Intel.

Destination: this is the file where data read off the media will be stored. Since DrDD can backup partial areas, the default naming scheme will include, as a reminder, range information. Two formats are supported: one pure raw format, created with the .dd extension, and a PhotoRescue specific format, created with the .cib extension.

Range Selection: there are two ways to select the portion of the damaged media that DrDD will attempt to read: by size, or by allocation units (commonly referred to as sectors). In this case, we are attempting to read 175.000 MBs starting at 100.000 MBs and ending at 275.000 MBs. The default selection is to backup the whole device. Coarse interval selection is achieved through the MBs interval boxes. Fine grained interval selection is achived through the Sectors interval boxes. This feature would typically be used with a hard drive that suffers from bad sectors or a memory card that locks up because if a defective memory bank.

Read Direction: the creation of the copy can be done by reading the device forward or backward. The default copy direction is forward. Copying backward may be interesting because, in some cases - typically hard drives - it disables the look ahead buffer and therefore reduces the risk of lock up on a full track.

Log Window: will display messages about the program's operation.

Last Log: this button will call up the last log. Since a hardware crash may completely lock a system, it may be difficult to determine exactly where the damaged area begins. If a lock up occurs, the system should be reset, and the log viewed to determine the last safe sector to read.