R-Studio Technician versions can perform three types of object imaging:

• Linear imaging (from the drive beginning to its end)
• Runtime imaging (drive imaging in parallel with other drive operations)
• Multi-pass imaging (performing drive imaging through several passes)

Their comparison chart can be reviewed in our article, Linear Imaging vs Runtime Imaging vs Multi-pass imaging.

Conventional drive imaging programs read a drive sequentially from the beginning to the end by sector blocks, or groups of consecutive drive sectors, that are read in one go. When they encounter areas with bad or slow sectors, they still try to read them entirely. That may lead to a complete loss of data from such blocks, or cause the program to switch to reading individual sectors - thus greatly reducing reading speed. Moreover, the program may eventually get stuck into areas while reading those bad sectors again and again, though such intensive reading from bad sectors may severely damage the drive surface, its heads, and other drive mechanics. As a result, the drive may die before the program starts reading data from the good parts of the drive.

Instead, a program using multi-pass imaging tries to extract data from drive's good parts first, ultimately leaving the bad and slow areas for later. Shortly thereafter, when it comes to a bad or slow sector block, it drops it and jumps to another area until it finds a block with no bad or slow sectors. It then continues reading data until it runs into another bad or slow block, where the process repeats. When the good areas have been read, the program starts reading data from slow and bad sectors. This approach maximizes the amount of data that can be recovered from a failing drive.

R-Studio can perform multi-pass imaging in its Technician and T80+ versions. Moreover, multi-pass imaging can be used together with special data recovery hardware like DeepSpar USB Stabilizer, which greatly increases chances for successful data recovery - even from drives in very poor hardware condition.

The multi-pass imaging implemented in R-Studio consists of four phases:

PHASE 1. Copying good data from the drive.
R-Studio reads data from the drive by sector blocks in this phase. The phase is performed in several steps.

Step 1. R-Studio reads data from the drive until it runs into a block with at least one bad sector. Then it skips a certain number of sectors and tries to read data at the new position. If it runs into another block with a bad sector, it increases the number of sectors to skip and repeats the process until it finds a block with no bad sectors. Then R-Studio continues reading the data until it runs into another block with a bad sector.

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R-Studio processes slow sectors in the same way.

When this step is completed, R-Studio has read data from most good areas and found the front blocks (edges) of bad and slow sector areas.

Step 2. R-Studio finds the rear edges of bad sector areas. It reads the skipped area from its rear, working backwards until it runs into a block with a bad sector. Then, R-Studio jumps to another bad sector area and the process is repeated until all bad sector areas have been processed.

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When this step is completed, R-Studio has read data from some good areas and detected the front and rear blocks (or edges) of all bad sector areas.

In the next two steps, R-Studio processes slow sector areas without checking read speed against minimum I/O rate.

Step 3. R-Studio reads data from slow sector areas. It does this similarly to the process for bad sector areas.

It reads a slow sector area by blocks until it runs into a block with a bad sector. Then it skips a certain number of sectors, and so on, until it finds a block without bad sectors. It then continues reading data until it runs into another block with bad sector, and the process is repeated until all slow sector areas have been processed.

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Once this step is completed, R-Studio has effectively read data from all slow sector areas and detected the front blocks, or edges, of all bad sector areas within slow sector areas.

Step 4.. R-Studio finds the rear edges of bad sector areas in slow sector areas. It reads the skipped area from its end, working backwards until it runs into a block with a bad sector. Then, R-Studio jumps to another bad sector area and the process is going on until all bad sector areas have been processed.

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Once this step is completed, R-Studio has read some new data from slow areas and detected the front and rear blocks, or edges, of all bad sector areas within slow sector areas.

Step 5.. R-Studio tries to read all skipped sector blocks. This is done without skipping bad sector blocks and checking read speed against minimum I/O rate.

When Phase 1 is completed, R-Studio has read most of the readable data and detected front and rear edges of all bad sector areas.

In the upcoming phases, R-Studio tries to read the rest of data and does that sector by sector rather than by sector blocks.

PHASE 2. Trimming.
R-Studio detects the front and rear sectors of bad sector areas in this phase. It reads the front block of a bad sector area by sectors until it runs into a bad sector. Then it reads the rear block of the bad sector area and works backwards until it runs into a bad sector.

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When this phase is completed, R-Studio has read some new data from bad sector areas and detected the front and rear sectors of all bad sector areas.

PHASE 3. Scraping.
R-Studio tries to read data from bad sector areas sector by sector in this phase. There may be good or bad sectors in these areas.

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When this phase is completed, R-Studio has read all readable data from the entire drive.

PHASE 4. Retrying (optional).
R-Studio tries to read data from bad sectors through several attempts in this phase.

You may control parameters of multi-pass imaging on the Bad sector processing tab of the Create Image dialog box.

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R-Studio shows multi-pass imaging progress and the statistics of multi-pass imaging during the process.

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Conclusions:
Multi-pass imaging is a very powerful tool for creating images of failing hard drives. In addition to extracting more good data from the drive, it also minimizes wear and tear of drive hardware - greatly reducing chances for the drive to completely fail during the process of its imaging. R-Studio implements in the most advanced way, ultimately providing a very flexible adjustment for all necessary imaging parameters.