Question Question about "reallocated sectors count" ?

~cw

Mar 31, 2022
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Those sort of reallocated sector counts are typical of a drive which will probably start to exhibit filesystem errors in the next couple of months. Backup the data while the drive still works, then if it's still in warranty, send it back for a replacement.

I recently had to do exactly this for some Ironwolf drives whose reallocated sector counts reached ~250 before starting to cause problems with filesystem read/writes. I backed the data up just in time before one of them started to constantly error when in use. I also had a pair of ~10 year old WD Green drives which had been spinning for almost their whole life, one had about 140 reallocated sectors but worked OK until I replaced it.

At work, I found a machine which was running very slowly - in use since about 2012, its old HDD had several hundred MILLION reallocated sectors. I was amazed it was working at all! Its performance was utterly terrible. I don't know what caused it to fail so badly but I was just able to clone the drive to a new SSD before throwing it in the trash.

Allocated sectors starting to increase is always a good indication that the drive is not going to last much longer, so save your data and replace.
 
At work, I found a machine which was running very slowly - in use since about 2012, its old HDD had several hundred MILLION reallocated sectors.
100 million sectors would amount to 50GB. I can't see how that would be possible.

I suspect that the raw value would look a lot less frightening if it were expressed in hexadecimal. For example, some Toshiba models had reallocated sector counts which actually consisted of 3 hexadecimal numbers.
 

~cw

Mar 31, 2022
39
3
45
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100 million sectors would amount to 50GB. I can't see how that would be possible.

I suspect that the raw value would look a lot less frightening if it were expressed in hexadecimal. For example, some Toshiba models had reallocated sector counts which actually consisted of 3 hexadecimal numbers.
Well, on a 250 GB disk with an OS partition and lightly used storage partition, not unrealistic ;-) CDM diligently reported the sectors, I was inclined to believe it... The disk ran like an LTO3, it was so slow :ROFLMAO:

 
Well, on a 250 GB disk with an OS partition and lightly used storage partition, not unrealistic ;-) CDM diligently reported the sectors, I was inclined to believe it... The disk ran like an LTO3, it was so slow :ROFLMAO:
Hitachi was the other example I was thinking of. When you convert the reallocated sector count to hexadecimal, you get a number which actually consists of two 16-bit numbers:

107873993 = 0x66E06C9 -> 0x066E / 0x06C9​

The actual number of reallocated sectors is either 0x06C9 (= 1737) or 0x066E (= 1646).

No drive has 50GB allotted for spare sectors. The grown defect list (G-list) is a firmware module which is stored in a hidden, reserved System Area (SA) on the platters. This module is very small. It probably only handles a few thousand sectors. (I can find out the exact amount if you are interested.)
 
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~cw

Mar 31, 2022
39
3
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Hitachi was the other example I was thinking of. When you convert the reallocated sector count to hexadecimal, you get a number which actually consists of two 16-bit numbers:

107873993 = 0x66E06C9 -> 0x066E / 0x06C9​

The actual number of reallocated sectors is either 0x06C9 (= 1737) or 0x066E (= 1646).

No drive has 50GB allotted for spare sectors. The grown defect list (G-list) is a firmware module which is stored in a hidden, reserved System Area (SA) on the platters. This module is very small. It probably only handles a few thousand sectors. (I can find out the exact amount if you are interested.)
Ah so it was hex representation. Honestly given the performance I assumed the parity in the raid it was a member of was handling the problem - just about - and didn’t bother to do those conversions to see ;) There was evidently more than one issue with that drive.
Sorry for hijacking OP’s thread with this anecdote, it would be interesting to know the capacity for reallocated sectors though.
 
Your model is HDS721025CLA382 (HGST Deskstar 7K1000.C).

This is the product manual:

Hard Disk Drive Specification for HGST Deskstar 7K1000.C, HGST Ultrastar A7K2000, HGST CinemaStar 7K1000.C:

https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/eol/cinemastar-series/product-manual-cinemastar-deskstar-7k1000-c-ultrastar-a7k2000-oem-spec.pdf

Here are two firmware resource dumps for the 500GB version:

http://files.hddguru.com/download/PC-3000-UDMA Support/Hitachi-IBM/Hitachi HDS721050CLA662-JP2OA41A-JP1572JE2P59GK.rar
http://files.hddguru.com/download/PC-3000-UDMA Support/Hitachi-IBM/Hitachi HDS721050CLA662-JP2OA41A-JP1572FN204YTK.rar

The RDMT.rpm module is the grown defect list. Its size is 32KB. Unfortunately it's empty in both cases, so I can't work out its structure. However, if we assume that each defect would be described with 8 bytes, then that corresponds to a maximum of 4096 reallocations. I guess it is possible for an entry in the list to correspond to an entire track, so that might allow for more sectors.
 
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~cw

Mar 31, 2022
39
3
45
1
Your model is HDS721025CLA382 (HGST Deskstar 7K1000.C).

This is the product manual:

Hard Disk Drive Specification for HGST Deskstar 7K1000.C, HGST Ultrastar A7K2000, HGST CinemaStar 7K1000.C:

https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/eol/cinemastar-series/product-manual-cinemastar-deskstar-7k1000-c-ultrastar-a7k2000-oem-spec.pdf

Here are two firmware resource dumps for the 500GB version:

http://files.hddguru.com/download/PC-3000-UDMA Support/Hitachi-IBM/Hitachi HDS721050CLA662-JP2OA41A-JP1572JE2P59GK.rar
http://files.hddguru.com/download/PC-3000-UDMA Support/Hitachi-IBM/Hitachi HDS721050CLA662-JP2OA41A-JP1572FN204YTK.rar

The RDMT.rpm module is the grown defect list. Its size is 32KB. Unfortunately it's empty in both cases, so I can't work out its structure. However, if we assume that each defect would be described with 8 bytes, then that corresponds to a maximum of 4096 reallocations. I guess it is possible for an entry in the list to correspond to an entire track, so that might allow for more sectors.
Very interesting, thanks for the follow-up with more info about the specifics of that model drive. HDDGuru is a site I am preparing to spend unhealthy amounts of time reading. :D
 

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