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 Post subject: Bad Sectors
PostPosted: March 18th, 2018, 10:05 
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Joined: March 18th, 2018, 9:46
Posts: 4
Location: England
I have quite a few Qnap NAS. After a few years some hard drives went abnormal, and had bad sectors. I purchased new of the same type and size and hot swapped them, all fine.

I put the old drives in caddies and ran HDDRegenerator because 'why not' I would only have destroyed them anyway. Thing is that a few of the drives were acutely repaired by this snake oil program. I have had them in a PC continuously reading and writing to the disk, filling it and deleting and they seem good (not to go back in my NAS though) and new ones are cheap as chips these days anyway.

HDDRegenerator however cannot fix about half of the drives, it says its regenerated the sectors, but smart still claims they are either pending - uncorrectable - or already swapped. Other times it times out, so I guess these drives are really really broken!

I would like to know how come this program actually managed to relocate sectors on some of the drives and not others even though I did a zero out 2 pass format - and what are they these fixable sectors anyway ?

And one last question if I may - why did HDDRegenerator manage to 'fix' (a loose term I know) the sectors when the bad block check of the QNAP did absolutely nothing ? If the blocks could have been swapped out then why did the NAS not do it ?

Many Thanks if you got to the end, and even more thanks if you can shed some light.


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 Post subject: Re: Bad Sectors
PostPosted: March 19th, 2018, 18:14 
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Joined: October 16th, 2013, 13:21
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Location: Brazil
The fixed ones were those with a small number of bad sectors, and that could be replaced by the spare ones.

Those with the defects not hidden by hdddegenerator were those that had a lot of bad sectors, weak heads or other problems.

The bad block checking on the NAS replaces blocks at the logic level of the way it formats the hdds. Not inside the disks, i.e., it doesn´t do the read-write-read hdddegenerator does. The NAS doesn´t try to fix disks, it just signals they are going to fail and refuses to use them.


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 Post subject: Re: Bad Sectors
PostPosted: March 20th, 2018, 10:49 
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Joined: March 18th, 2018, 9:46
Posts: 4
Location: England
Oh right - I think I understand (a little) now. So the NAS detects, and remembers where they are and does not attempt to read or write to them!

Sounds like a good solution !

Thanks for the info.

Hang on, just re-read your post, I now think you are saying, that the NAS sees bad blocks and wants me to replace the drive, and makes no attempt to write around the bad blocks ?

Presumably for data safety.


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 Post subject: Re: Bad Sectors
PostPosted: March 20th, 2018, 12:08 
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Joined: October 16th, 2013, 13:21
Posts: 680
Location: Brazil
Some of both things.

The NAS detects when some error occurs, then mark it in its filesystem. It doesn´t try to fix the hard disk. It it considers there are too much errors, then the NAS signals the drive as bad.


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 Post subject: Re: Bad Sectors
PostPosted: March 20th, 2018, 17:15 
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Joined: March 18th, 2018, 9:46
Posts: 4
Location: England
Thanks for the info, makes me wonder how many of these 'seller refurbished' drives have had the HDDRegenerator' treatment.

My 'repaired' drives all report S.M.A.R.T as good, with no relocated sectors or anything to suggest its been fixed. The only thing I can see is that an exact same 'good' drive seems to report a slightly larger capacity than the 'repaired' drive not sure why though.

I'm well chuffed with the results, I might stick them in a USB enclosure and use them for movies or something like that.


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 Post subject: Re: Bad Sectors
PostPosted: March 20th, 2018, 17:42 
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Joined: September 8th, 2009, 18:21
Posts: 10482
Location: Australia
Umpa wrote:
The only thing I can see is that an exact same 'good' drive seems to report a slightly larger capacity than the 'repaired' drive not sure why though.

The smaller drives may have a HPA. If so, you can remove it with tools such as MHDD, HDAT2, HDD Capacity Restore Tool.

_________________
A backup a day keeps DR away.


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 Post subject: Re: Bad Sectors
PostPosted: March 21st, 2018, 5:28 
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Joined: March 18th, 2018, 9:46
Posts: 4
Location: England
Both drives were the same make and model. Sorry I don't know what a HPA is.
Edit: Googled it. Host Protected Area. Could be the reason I guess. I need to read up on it. This is an interesting topic, I am enjoying tinkering with what would be a throwaway drive.


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