Bad Sectors

I had always thought of bad sectors as being physical damage, and therefore cause for an RMA, but I found some old forum threads on the subject, one of which said this:

bad sectors are usually caused by cross-linked files which are a result of the operating system overwriting a portion of one file with another file. Potential causes of cross-linked files are turning off or restarting your computer without exiting Windows or by not regularly defragmenting your hard disk. Another reason is when the heads make contact with the hard disk platter(s).

My computer has had more than it's share of forced restarts, due to freezes where the only alternative was to use the reset switch. I knew that this could cause corrupted data, but never thought that it would also cause bad sectors.

If this is true, how would one determine if the problem is of a physical or a software based origin?

Run a 'Defrag & Optimize' programe with the 'Auslogics Disk Defrag' free defrag software. (this run is a humble defrag run, it is just more complicated) After that your bad sectors should have gone (or moved) if they were software based errors.

Most of what I found Googling were forum threads, therefore not necessarily definitive:

bad sector causes - Google Search

This statement from Wikipedia:

A bad sector is a sector on a computer's disk drive or flash memory that cannot be used due to permanent damage (or an OS inability to successfully access it),

seems to allude to it, although it is not clearly defined.

Bad sector - Wikipedia, the free encyclopedia

The first paragraph of this article seems to confirm it:

http://www.datarecovery.com.sg/data_..._hard_disk.htm

A bad sector is a sector on the drive that couldn't be read when it was called into service. The drive will attempt to read it again (or the defragmenter). If it is unreadable once again, it will be marked bad 4ever.

The drive the has two available options, depending on its overall condition and age - replace the bad sector with the backup sectors every drive always has - and if it can do that, the bad sector doesn't appear in the count (but you can see this kind of event in SMART under a different category).

If it has run out of backup sectors, you get a bad sector you get to know about.

As far as the "spare sectors" that are provided for this purpose...where are they? Are they interspersed everywhere, among the regular sectors, or in a block set apart from the others? If the latter, that would be the cause of possible fragmentation. Once that a sector is marked bad, is it totally ignored in the future by diagnostics, or will it always be shown as a bad sector? If the latter, then there is no direct means to know if it has actually been remapped or not. I suppose that the only way to do so, would be to totally reformat the drive, and see if the bad sector continues to appear.

seekermeister said:

As far as the "spare sectors" that are provided for this purpose...where are they? Are they interspersed everywhere, among the regular sectors, or in a block set apart from the others? If the latter, that would be the cause of possible fragmentation. Once that a sector is marked bad, is it totally ignored in the future by diagnostics, or will it always be shown as a bad sector? If the latter, then there is no direct means to know if it has actually been remapped or not. I suppose that the only way to do so, would be to totally reformat the drive, and see if the bad sector continues to appear.

AFAIK, most disks keep a few spare sectors on each cylinder and at least one spare cylinder. To the extent possible, a bad sector will be mapped to another sector on the same cylinder, or one located close by.

Theres another concept called Sector slipping in which all sectors between the bad sector and the replacement sector move down by one.

I think the drive firmware has control over bad sectors so you can't do anything about it if it's really bad, although I'm not sure. Sectors that were unreadable for some temporary reasons will probably be succesfully read on second pass anyway.

The reason for my interest is to be able to determine if a bad sector is actually cause for an RMA or not. I got the impression that some file system problems might not be corrected properly by chkdsk, SFC, etc. and would remain until doing a low level format of the drive. Even though that would be a step that I would take prior to an RMA, it is not one that I would want to do, unless convinced that an RMA was necessary. Therefore, it would be good to be able to 100% determine the situation beforehand.

Teerex,

Are you saying that if a sector remains marked bad, after a second run of a diagnostic, that it definitely is a permanent flaw of the drive?

The best route to RMA would be running the concerned diag tool and failing the short and long and other tests. Save a copy of the test results.

Until then, unless the disk is sluggish or there're random read/write errors, it should be fine. As usual, keep your data backed.