Weak Sectors

[soyo]

Hey hdsentinel

I wanted to ask you about weak sectors, and what do they mean, when they are reported by HD Sentinel?

The reason I ask is this. The HD Sentinel shows me there are 13 weak sectors on the drive. I checked the hard drive with HD Tune with Error Scan, and there are Damaged sectors found, and what do you know, there are 13 of them. However the HD Tune shows them as "Damaged sectors", which means bad sectors?

Anyways, I would really appriciate some more explanation from you about this, and also if this validates me asking for replacement of the hard drive, under warranty policies.

cheers
Lucas

[hdsentinel]

Hi Lucas,

Thanks for your question.

Basically the "weak" sectors are not bad sectors. Most of the time, they even not related to hard disk problems as non-standard shutdown (reset/power failure) can cause this status for a particular sector.
The drive marks these sectors as "pending" for reallocation. So on further disk usage these sectors may or may not be reallocated.
Usually if you perform a Disk -> Surface test -> Read test, it properly shows the location of these sectors (I wonder why you used other software for that? )
Also Disk -> Surface test -> Reinitialise disk surface test forces the hard disk to verify the status of the sector and re-allocate (to prevent further using of that sector) OR to remove this "pending" (weak) status if the sector seems to be usable.

As I wrote, this status may be caused by something which is independent from the hard disk. So after using Disk -> Surface test -> Reinitialise disk surface, the sectors will be likely fixed and the errors will be removed from the text description (and the health% will increase as well).
Because of that, no warranty replacement is required this time.

[soyo]

Outstanding response as awlays hdsentinel.

One further question. When I look into this tool you directed me to, it tells me all the data will be removed from the hard drive, which means I have to first copy the content out of the disc. Is this true?

The reason I wonder about it, is that you said before those sectors are "pending" for realocation, which means that in some time, they will be moved automaticaly, which won't overwrite my entire harddrive, hence I won't have to move the data away from it for this process to occur.

I was wondering, why this test is behaving in this fashion?

cheers
Lucas

[hdsentinel]

Yes, as you wrote: you will need to backup the data from the hard disk first.

Yes, exactly: write command(s) directed to the pending sectors should force the drive to re-examine their status and fix them (either by reallocation or by removing the pending ("weak") status). However, sometimes simple write commands may not sufficient, this is why the "Reinitialise disk surface" method is preferred as it uses special overwrite patterns and methods to force the drive to take the required actions.

The problem is that when the hard disk has a working file system, Windows prevents writing to the affected physical sectors. (More precisely Microsoft introduced this limitation in Windows Vista to protect the file system). So basically it is not a limitation of the software, but the OS.

You are correct: if you do not take any actions, the pending sectors may be fixed with time, when the affected sectors will be overwritten (may require many overwrite passes as I wrote above). If the sectors are not related to any files/directories/MFT (affect only empty, currently unused area) you may try some methods (for example filling the drive completely by copying huge files onto it). If you're lucky, some (or all) of the sectors will be corrected and the number of weak sectors will decrease.
However, the best would be completely eliminate them as they may cause further problems and risk of both data integrity and system stability.

[soyo]

Thanks for extensive explanation hdsentinel!

Doing the test as we speak. Got one follow up question if you don't mind. When the drive stumbs upon a bad sector, it is trying(correct? I mean some bits from that sector will be a mess?) to move this data to a portion of spare sectors, and at this time there is 1 more realocated sector.

What happens here in this case? When there is weak sector, does it mean the situation is simmilar to the bad sector -> realocated sector scenario? Or it just means that the sector is weak but STILL all it's bits are readable as they were originaly written, so it's more of a warning message.

Would you mind explaining those 2 paragraphs as well?

cheers!
Lucas

[hdsentinel]

Excuse me, I'm not sure if I understand your questions properly.

Do you have the "Reinitialise disk surface" test running?
If so, the weak/pending sectors reported should be corrected. As I wrote, if required, the sector will be re-allocated (so the original sector will not be used again, but then the spare area will be used for all further reads and writes).

But I suspect there will be no need to reallocation this time. It means that the drive checks if the sector can be used without problems, this is why the "Reinitialise disk surface" function is required: it uses special overwrite patterns so the drive can surely check if the sector contents can be read back and the CRC checksum is correct.
If this happens, the sector can be used without problems in the future - so the error will be removed from the text description.


If the drive experiences a BAD sector (this is completely different, as this is the reallocated sector), it is a completely different thing. This is what is never used again. If you see "bad sector" reported by chkdsk, it is also a completely different thing: it is a logical bad sector, related to the current file system only. It means that the "Reinitialise disk surface" test completely fixes that.

Let's see the result of the test. If things will be fine, the surface map after this "Reinitialise disk surface" test will show green blocks only and the errors will be removed from the text description. You may even save the surface map (with the floppy button in the upper right corner) and send it to info@hdsentinel.com address. Also you may use Report menu -> Send test report to developer option so I can check the results of the test and may advise if the test reveals some further problems.

If you have other question(s) or if I did not understand the questions properly, please let me know.
You may also consider:
- click on the "?" next to the text descriptions
- read the http://www.hdsentinel.com/faq.php#health section
about "bad sectors".

[hdsentinel]

.... it uses special overwrite patterns so the drive can surely check if the sector contents can be read back and the CRC checksum is correct....

Of course if this happens, this means that there are NO defective bits in the proper sectors.

[soyo]

Excuse me, I'm not sure if I understand your questions properly.

Do you have the "Reinitialise disk surface" test running?

Correct. Sorry to not make it clear enough. BTW, you were not lying that it tends to be pretty long. It shows me 20 more hours on 500GB hard drive

If so, the weak/pending sectors reported should be corrected. As I wrote, if required, the sector will be re-allocated (so the original sector will not be used again, but then the spare area will be used for all further reads and writes).

But I suspect there will be no need to reallocation this time. It means that the drive checks if the sector can be used without problems, this is why the "Reinitialise disk surface" function is required: it uses special overwrite patterns so the drive can surely check if the sector contents can be read back and the CRC checksum is correct.
If this happens, the sector can be used without problems in the future - so the error will be removed from the text description.


If the drive experiences a BAD sector (this is completely different, as this is the reallocated sector), it is a completely different thing. This is what is never used again. If you see "bad sector" reported by chkdsk, it is also a completely different thing: it is a logical bad sector, related to the current file system only. It means that the "Reinitialise disk surface" test completely fixes that.

Let's see the result of the test. If things will be fine, the surface map after this "Reinitialise disk surface" test will show green blocks only and the errors will be removed from the text description. You may even save the surface map (with the floppy button in the upper right corner) and send it to info@hdsentinel.com address. Also you may use Report menu -> Send test report to developer option so I can check the results of the test and may advise if the test reveals some further problems.

If you have other question(s) or if I did not understand the questions properly, please let me know.
You may also consider:
- click on the "?" next to the text descriptions
- read the http://www.hdsentinel.com/faq.php#health section
about "bad sectors".

I will try to be more clear, sorry for the inconvinience. Also don't want to waste your time with any reports, as it's no big deal, really.

As for my questions, they were more of a general questions about the bad sectors/weak sectors/realocated sectors, not questions in regards to the test.

Doing the test as we speak. Got one follow up question if you don't mind. When the drive stumbs upon a bad sector, it is trying(correct? I mean some bits from that sector will be a mess?) to move this data to a portion of spare sectors, and at this time there is 1 more realocated sector.

What I was asking about over here, is the case when the disc finds a bad sector. In that bad sector, there is data written(so some bits). But bad sector means that some(or all?) of that data is corrupted, correct? So what happens at this point, when the disc recognises a bad sector, it tries to move the data stored in that sector to one of the spare ones.

Furthemore, this means, that anytime there is a sector realocated, some portion of that sector(data) is corrupted, and is not the same as original, correct?

Or maybe the hard drive technology is smarter in protecting our data?

What happens here in this case? When there is weak sector, does it mean the situation is simmilar to the bad sector -> realocated sector scenario? Or it just means that the sector is weak but STILL all it's bits are readable as they were originaly written, so it's more of a warning message.

In here, I was asking same (general) stuff, but in regards to weak sectors as oppose to bad sector. Does it also corrupt the data, or the case here is different?

Sorry for not being clear enough before. I hope that will do

cheers
Lucas

[hdsentinel]

Correct. Sorry to not make it clear enough. BTW, you were not lying that it tends to be pretty long. It shows me 20 more hours on 500GB hard drive

Yes, it is very intensive and really take much time

What I was asking about over here, is the case when the disc finds a bad sector. In that bad sector, there is data written(so some bits). But bad sector means that some(or all?) of that data is corrupted, correct? So what happens at this point, when the disc recognises a bad sector, it tries to move the data stored in that sector to one of the spare ones.

Yes, exactly as you wrote: when the bad sector is found, the drive tries to read back the data from that sector and uses the CRC mechanism to reconstruct the data stored there. Then the drive copies this "data" to the spare area, marks the original location as bad and then all further reads and writes are re-directed to this spare area.
The success rate depends on the drive, the actual situation, the problem with the hard disk, etc.

Furthemore, this means, that anytime there is a sector realocated, some portion of that sector(data) is corrupted, and is not the same as original, correct?

Exactly as you wrote: during the reallocation process, the data may not be read and may not be corrected (there are limitations in the technology). It means that the re-allocated data may be corrupted, it is different compared to the original.

Or maybe the hard drive technology is smarter in protecting our data?

The technology has lots of protections, for example the CRC mechanism I mentioned above. It can detect and correct errors if some bits are corrupted but if the number of corrupted bits in the affected sector is larger than this, the data can't be corrected at all.

Sorry for not being clear enough before. I hope that will do :)Lucas

I'm sorry - I just did not understand correctly, I thought you were asking for this particular situation (not in general).

[soyo]

Yes, exactly as you wrote: when the bad sector is found, the drive tries to read back the data from that sector and uses the CRC mechanism to reconstruct the data stored there. Then the drive copies this "data" to the spare area, marks the original location as bad and then all further reads and writes are re-directed to this spare area.
The success rate depends on the drive, the actual situation, the problem with the hard disk, etc.

I see now. It's a bit frightnening though, as I always thought the hard drive is the safest way to storage data, in a sense, that until there is no spare sectors left the data is intact. Thanks for the info.

I'm sorry - I just did not understand correctly, I thought you were asking for this particular situation (not in general).

Don't worry about it. You shouldn't appologise, instead I should thank you for the time taken in explaining the things I asked. So thank you!

Lucas

[hdsentinel]

Excuse me, in general, you do not need to be frightened.
This mechanism is only one of the protection methods used by hard disks and I can confirm that yes, hard disk drives are the safest way for data storage - IF the operating environment for the drive is safe. I mean if the power input, the operating temperature is correct, there is no vibration / shock, the cables and connections are correct, the data stored on the drive is safe.

Also before first using any new hard disk, I always recommend intensive testing by

1) Disk -> Short self test
2) Disk -> Extended self test
3) Disk -> Surface test -> Read test
4) Disk -> Surface test -> Reinitialise disk surface

If these do not show problems, the drive is 100% after the tests and the operating environment is fine, you can be sure that your data is safe and will be available for a long time.

[soyo]

Excuse me, in general, you do not need to be frightened.
This mechanism is only one of the protection methods used by hard disks and I can confirm that yes, hard disk drives are the safest way for data storage - IF the operating environment for the drive is safe. I mean if the power input, the operating temperature is correct, there is no vibration / shock, the cables and connections are correct, the data stored on the drive is safe.

Also before first using any new hard disk, I always recommend intensive testing by

1) Disk -> Short self test
2) Disk -> Extended self test
3) Disk -> Surface test -> Read test
4) Disk -> Surface test -> Reinitialise disk surface

If these do not show problems, the drive is 100% after the tests and the operating environment is fine, you can be sure that your data is safe and will be available for a long time.

Excelent

Thanks hdsentinel for clearing that up.

Lucas

[edwie9]

Hi Hdsentinel,

I followed all your discussion with the other guy, and did everything you discussed step by step. My problem is that a i have a very slow hdd, 320gb by samsung. When i first ran Hdsentinel, it showed me 50 weak sectors, with the short test, but when i repeated the test after 2 weeks it showed around 160. Well, i did the Disk -> Surface test -> Reinitialise disk surface on my hdd wich i did put it on an external drive, and after approximately 24 hours it raised health to 90% and only 16 weak sectors left and also more than 1000 days estimated remaining timelife. This is a picture of the results. http://imageshack.us/f/803/resultsny.jpg/
So, my question is, is it necessary for another test as time as there are 16 weak sectors remained yet?
Is it possible now, to reinstall windows 7 and to have a normal hdd, not a slow one? I mean, does the reduction of weak sectors help my hdd to work normal? (It took 5-10 minutes to log in windows, when in a normal log in it takes 30-60seconds)
My final question is, is it worth it, or should i buy a new hdd? Can it work "normal" again for some time at least?
Thanks!

[hdsentinel]

> So, my question is, is it necessary for another test as time as there are 16 weak sectors remained yet?

Yes. The previous test (the Read test) revealed the problems - as the drive accessed the complete surface, it found and logged all such sectors.
The Reinitialise disk surface test repaired most of the problems, fixed most weak sectors, but it seems there may be some still on the drive.
So you may need to re-run the test to completely eliminate the problem.

However, it is possible that the current environment (the power and/or data cables, connection) is the source of the problems. This would confirm this (relative) high number of weak sectors, the fact that first running the Reinitialise disk surface test did not fix all problems - and may cause the slowness as well. If this is true, you may expect further weak sectors at later use which reduces both stability and performance.

So I'd recommend to test the drive in a different computer with these functions, by different power supply, different cables. Then hopefully the remaining 16 weak sectors would be fixed.

> Is it possible now, to reinstall windows 7 and to have a normal hdd, not a slow one?

It is possible - the current location of the weak sectors may still cause slowness.
So I'd recommend to try to fix ALL such weak sectors by re-running the Reinitialise disk surface test (possibly in a different computer) and then check Disk -> Surface test -> Read test. If this goes well, no (new) weak sectors reported and the disk performance is correct (depending on the drive), I'd install a fresh OS but not in the current situation.
If you prefer, you can send/upload the "Temperature and transfer speed" graphs after this READ test, just to check the drive performance.

> I mean, does the reduction of weak sectors help my hdd to work normal?

Yes. If there are no weak sectors (and the cables/connections fixed - as these may be related to the current problems), you should expect a working, fast drive again.

> My final question is, is it worth it, or should i buy a new hdd? Can it work "normal" again for some time at least?

It is absoltely worth it. In most cases the weak sectors usually independent from the drive and by using Reinitialise disk surface test, they could be fixed (maybe partially for the first time). Then, if the drive has no other issues, it should work without problems - with full possible performance.

If you prefer, you can use Report -> Send test report to developer option, even many times (eg. now and after some tests). This way it is possible to check the full status of the drive, the change of the reported problems.

[edwie9]

Thanks a lot!
I just came home and left my laptop on, with the external drive connected on it. I don't very understand, but when i left it showed me 16 weak sectors, and now it's showing 26 of them.. i didn't do anything at all with the hdd, it just was connected to the laptop... Does it mean anything, the fast increase of the weak sectors in just a couple of hours (4-5hours) ? I am asking because it's impossible for me at the time to find another computer to run the test, and so if it is somthing else causing this, i don't have to run the 24 hours test again
Thank you very much for your help!

[hdsentinel]

This would even more confirm that the problem is related to the cable/connection issue: the drive may not operate properly because of the connection and/or the cable.

Is it a 2.5" external hard disk?
Do you use a double Y USB cable which is connected to 2 USB slots? If not, the power provided by the single USB slot may not be enough for the drive to operate properly - and this could be the original cause of the troubles.

See Support -> Knowledge base -> Hard disk cases for more information, the article at http://www.hdsentinel.com/hard_disk_case_spin_retry.php
shows this cable and other issue which may be also related to power.