> After read the section of the FAQ you suggested, it seems the best option is to use the Surface Test => Read test option. Is that correct?
The FAQ page shows the _combination_ of the following tests:
1) Disk -> Short self test
2) Disk -> Extended self test
3) Disk -> Surface test -> Read test
4) Disk -> Surface test -> Reinitialize disk surface
https://www.hdsentinel.com/faq.php#tests
(Hard disk health is low or recently changed or I just installed a new (used) hard disk. How can I perform a deep analysis?)
as these perform both hardware and software based testing methods, verify disk components and their functionality in general and also verifies both read and write capabilities.
If you are really paranoid (like me) then I'd suggest to start both of the tests.
If time is an important factor then yes, the best is to use Disk menu -> Surface test -> Read test.
This verifies if the complete data area is readable, reveals possible problems when particular sectors can't be read (shows red blocks on the disk surface map) - or if they damaged (shows yellow blocks on the disk surface map) or just work much slower than expected (shows darker green blocks on the disk surface map).
This is usually enough - as if this read test completes and shows no problems, the health is 100%, then in almost all cases, we can be sure the drive is really perfect and can be used (especially if it's a new drive), there are no damages during shipment/installation of the drive.
> Also, the description for the read test says "Disk problems may remain hidden" is this something I should be worried about on a brand new disk?
In some rare very cases (but not on brand new drives) drive may seems working correctly: all sectors can be read - but it is not able to write data on the surface. No errors reported, just the drive does not really write the data (or written partially).
This is extremely rare situation, found on some (older) drives only.
Because of these, if we want to be 100% sure, it may be good idea to write and verify written data. For this, the Reinitailise Disk Surface test (or the Disk menu -> Surface test -> Write+Read test, especially with non-zero data to be written) can be useful - but may require long time on a high-capacity drive.
So the Disk menu -> Surface test -> Read test is usually enough - and you may perform other write-tests only if the read test shows error(s).
> How does the read test work on a blank disk? If there's nothing on the disk then what is it reading in order to verify that the sectors are stable?
Hard Disk Sentinel tests the "raw" data sectors by the tests, independently from the actual stored data.
If you start the test and click on the disk surface map (click on one of the 10000 small squares) you can inspect the raw contents of the sector (most of them contains zeroes on a new, empty drive).
This way Hard Disk Sentinel tests both the data area (even empty which will be used to store files/folders) and also sectors outside the actual data area: partition table (MBR), unpartitioned space, possible partitions which are not readable under Windows (for example disks used in Linux / MAC systems).
This is why it is better than other methods (eg. chkdsk) which focuses on a partition only and may not reveal retries, slower areas and/or problems on a very new (unpartitioned or not initialized) drive.
For more information about disk tests, please see the Help:
https://www.hdsentinel.com/help/en/59_tests.html
(and sub-pages, eg.
https://www.hdsentinel.com/help/en/62_testfaq.html )