Surface Test

By using this test, the surface of the hard disk can be examined with different methods. Some of these methods are safe for the stored data but others are destructive: the stored information are permanently erased during the test operation.

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First it is required to select the hard disk and the test type to be started. The detailed description of the test are displayed upon selection, and the software displays how the test affects stored data. It is strongly recommended to read these information carefully before starting the test.

The following tests are possible:

READ Test – Reads the disk surface to verify if all sectors are accessible and readable.

The test is safe, it does not affect stored data.

Disk problems may remain hidden and revealed disk issues are NOT fixed (like with ScanDisk).

WRITE test – Overwrites the disk surface with configurable pattern. Forces the analysis of any weak sectors and verifies any hidden problems and fixes them by reallocation of bad sectors (this is drive regeneration).

Enables better use of the disk as after the test the spare area will be used instead of any problematic sectors.

WRITE + read test – Overwrites the disk surface with configurable pattern and then reads back sector contents, to verify if they are accessible and consistent. Forces the analysis of any weak sectors and verifies any hidden problems and fixes them by reallocation of bad sectors (this is drive regeneration).

Enables better use of the disk as after the test the spare area will be used instead of any problematic sectors.

Read + WRITE + read test (refresh data area) – Reads stored data from each blocks, writes back the contents and finally reads the information and compare with original contents. By the extensive test, an additional write cycle is used before writing back the contents to improve the efficiency of the error correction (drive regeneration).

The operation is usually safe for the stored information but data loss may occur if the system is not stable and/or upon power failure, overclocking, memory/power supply/cable problems and other factors.

The test can be used to refresh the data area of the storage device, without the need of complete erase but it is still recommended to backup important data before this test.

Reinitialize disk surface – Overwrites the disk surface with special initialization pattern to restore the sectors to default (empty) status and reads back sector contents, to verify if they are accessible and consistent. Forces the analysis of any weak sectors and verifies any hidden problems and fixes them by reallocation of bad sectors (this is drive regeneration).

Enables better use of the disk as after the test the spare area will be used instead of any problematic sectors.
Very intensive and time-consuming test, especially if the level (the number of overwrite cycles) is set to higher value.

The simple version of this test is usually (incorrectly) called as low level format by other tools. It can be effectively used to permanently destruct stored information (Navso P-5239-26 standard data destruction).

Each tests have different configuration options:

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In general, it is possible to configure the order of blocks to be tested and optionally the repeat count can be specified (so the software runs the same test on the disk two or more times) and it is possible to unmount all logical volumes (partitions) during the test. The latter is strongly recommended to prevent other software and the operating system from accessing the disk during test. System drive (containing the operating system, the root folder of the user or the swapfile of Windows) cannot be locked this way. Because of the actual system running, only read test (which does not affect stored data) can be used on a system drive.

Note: some tests and settings are available only in the Professional version of the software.

Note: to prevent unauthorized people from using the tests (especially the write tests) the software asks for the configured password before opening the test window.

Test Details

The software divides the data area to 10000 blocks, this is the surface map of the disk. When any block is clicked by the mouse, the contents of the sector under the selected block are displayed. This way it is possible to inspect the stored data and/or the written data after performing a write test. It is possible to examine the sector contents (and load back the results of a previously saved test) without starting a test by clicking the View button. This is safe for the stored data on the disk.

During the tests, Hard Disk Sentinel verifies the integrity of each sectors under the displayed blocks. If the block is accessible and can be processed without errors, they are shown by green color. Darker green color means that the sectors are slower and harder to process. The software filters out the effect of slower transfer times at the end of the disks. If sectors are harder to access and can be processed only after one or more retries, then the blocks are damaged but repaired, the software shows the corresponding blocks with yellow. Red color means that the block of sectors cannot be processed (read or written – according the selected test). Further WRITE test may be required to force the drive to reallocate the problematic sector(s) in the block.

In case of damaged or bad blocks found, it is recommended to examine the whole data surface with one or more WRITE test(s). During write tests, the software forces the hard disk to verify the status of the sectors on the surface and re-allocate them to the spare area. This way the original (bad) sector will not be used and all further read and write operations are redirected to the spare area. This is called regeneration. The resulting hard disk functions better, it is even possible that on following tests it shows only good (green) blocks because the bad sectors are no longer use. The side effect of regeneration is that the health of the drive may decrease because more and more problems are revealed. So regeneration usually does not improve the health (except if weak sectors were found and their status if stabilized).

During the tests if bad block(s) are found, it is possible that the software and/or the operating system is not responding during the re-allocation. This can take some minutes or even hours – depending on the size of the affected surface area. It is not recommended to cancel the operation and avoid reset or power off the computer. It is possible that the disk controller or its driver may disconnect the not responding disk so it disappears from the system. This is more likely possible with USB connection. If this happens, it is recommended to connect the hard disk directly to the motherboard or a different controller and start the test again.

Recommended use of the tests: start an extensive write test (for example with “reinitialize disk surface”) to verify if the disk surface is usable and force the verify and reallocation of any sectors at this time. Like the random seek test, the software measures temperature levels during these tests, so the highest possible temperature can be checked duri
ng this extreme load. The tests can be started on other type of storage devices (not only hard disks), for example on SSD devices, FLASH memory cards, pendrives also can be tested – and the “read – write – read” test can be effectively used to prevent data loss caused by the “forget” effect of the memory cells.

The tests can be useful even if the hardware tests stop with an error, not supported or not available.

Note: the unregistered version does not allow the starting of any test(s). It is only possible to view sector contents with unregistered versions.

Note: during the tests, software and the operating system running in the background may affect the performance (thus the resulting color) of each blocks. To minimise this effect, the software prevents the screensaver from starting, prevents the computer entering any standby or lower power management mode and using a higher priority. Anyway, it is recommended to close all other background operations during the test and repeat the test if the performance decrease effects a larger area (not only 1-1 blocks). The software has option to repeat the test to minimise this momentary performance decrease.


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The end of the usable data area is bad. The bad blocks form continuous areas, suspecting a serious surface problem. Notice the yellow damaged block near the lower left corner: it is neighbor of a bad block and will probably turn to bad at later use. Even non-damaged blocks are very slowly accessible. It is recommended to check the location of the first problematic block with the mouse pointer and create partition(s) which do not use the following area.

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The hard disk showed many problems. It stopped during reading and writing operations and its health was relatively low (30 %). There were different bad, damaged and slowly accessible blocks.

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The same disk after many “Reinitialize disk surface” tests. The weak sectors are fixed and the bad sectors are reallocated (the health decreased to 20%) but the overall surface is improved and the disk can still be used for some time (but not recommended to store important data because of the problems).

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A typical low health (22 %) hard disk. Many write tests (especially the re-initialise disk surface test) can improve the status but it is not recommended to use the first half of this drive (by creating partition(s) only at the second half).

Surface test