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 Post subject: Explaining Disk Check Results
PostPosted: December 31st, 2017, 17:15 
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Joined: May 26th, 2017, 13:03
Posts: 18
Location: Volgograd, Russia
Hello,

There are often high-pitched and screeching noises coming from the system block, and the system often shows errors. Can someone explain what the following figures mean?


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 Post subject: Re: Explaining Disk Check Results
PostPosted: January 7th, 2018, 0:32 
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Joined: November 22nd, 2017, 21:47
Posts: 309
Location: France
The 1TB is fine, the 320GB one has 11 sectors ("B" in hexadecimal) identified as bad (unreadable or readable with abnormal difficulty).
It's still a low figure (especially considering the high Power On Hours number), it can stay that way for a long time but it's recommanded that you clone it or transfer everything of value to another storage unit and use it for non-critical data from now on.


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 Post subject: Re: Explaining Disk Check Results
PostPosted: January 7th, 2018, 18:01 
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Joined: May 26th, 2017, 13:03
Posts: 18
Location: Volgograd, Russia
Thank you for the information. The age of the drive was shown in one software to be about 1,400 days. Perhaps that figure refers to the combined total amount of hours the drive has been in use. Since the drive is very old and did not load again, I have installed a newer disk.


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 Post subject: Re: Explaining Disk Check Results
PostPosted: January 7th, 2018, 18:35 
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Joined: November 22nd, 2017, 21:47
Posts: 309
Location: France
Quote:
On WD (modern ROYL) drives it's not recommended to run with pending sectors as if the pending list (RE-LO) grows too big there are chances for the drive to slow down considerably.... to the point of the data to get inacessible.


What particular range of models does “ROYL” refer to ?
In this particular case it's still far from being a severe issue which could lead to the kind of failure that you're mentioning – although I know that it can evolve pretty fast, especially if there are repeated access attempts to files containing bad sectors. Do you know precisely how big the pending list can grow before triggering that slowdown ?
Also, I've read a few threads about that “slow issue” on WD HDDs : apparently there's a fix for that, right ? HDDSuperTool seems to be able to fix it so it doesn't even require any hardware tool. Granted, it's quite advanced stuff, only known by specialists, but precisely, someone coming here for advice should be in “good hands” so to speak, and get thorough information rather than a “do this / don't do that” kind of reply. (This relates to my own experience as well – I've exposed a particular issue in detail, trying to learn something from it, and had replies like a pavlovian “don't use Seagate hard drives they're bad”... kinda frustrating !)


Quote:
If you transfer all data out of the 320GB drive and you confirm that the data is securly saved ...


How would you proceed to verify the files' integrity in such a case ? When copying files between healthy HDDs I always do a thorough comparison with WinMerge before deleting data from the source, but if the source has bad sectors, how to ensure that the transfer was flawless, or if it was not, how to know which files could be corrupted ?
Even with so few pending sectors it may be worth doing a full clone with ddrescue or HDDSuperClone, then using the LBA of the unreadable areas (if any) to identify the affected files (can be done with ddr_utilities with the logfile from ddrescue as input). But I've had a case where trying to access bad sectors using ddrescue considerably worsened the HDD's state in a matter of hours, even though, prior to that, I had been able to successfully copy everything but the affected files... So, if I had been making a full clone first, I may have recovered much less data than by proceeding like I did. (As I mentioned above, I asked about it here, but got no relevant reply.)


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... you can try to zero fill the drive or secure erase it in order to re-use the pending sectors or force them to go to the G-List and be swapped by spares.


In this case, considering the drive's age (power on hours), I'd say that it's unlikely that those sectors have been wrongly identified as bad and are in fact perfectly fine – but yeah, it's still worth a try. Although I've had cases where a bunch of sectors were marked as bad, appearing in the Pending Sectors list, then disappeared after a complete scan (Pending Sectors back to 0), only to reappear some days later, with others added later on, while the HDD wasn't even used, just staying idle. So it's safe to say that it's no longer safe to use in a safe way.
A HDD like this could still be used to store movies or music to play on a standalone device for instance, or to share them with friends (making a CRC or MD5 check after each copy for peace of mind). Then, as Ivan Drago would have said, “if it dies, it dies...” – those files on it were expendables anyway.


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 Post subject: Re: Explaining Disk Check Results
PostPosted: January 8th, 2018, 23:09 
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Joined: November 22nd, 2017, 21:47
Posts: 309
Location: France
Quote:
Very old WD drives did had a WDC MCU. Latest WD drives with WDC MCU were Arch-VI Cyl 32 and they were then replaced with Marvell MCU. The first WD drives on the market with Marvell MCU did had a slight diferent firmware than "modern" ROYL. There are just a bunch of families on the market that were Marvell based an NOT ROYL. You can identify ROYL drives by checking the modules of the firmware. Here : - http://yura.puslapiai.lt/files/wd/mhdd/wd_royl_rom.html but any recent WD drive that you will encounter will be ROYL.


I would guess that the O.P. (if that person is still stealthily lurking around here :) ) doesn't know what a “MCU” is, and neither do I... Maybe... “micro chip unit” ? (Just a guess, didn't search.)


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There is NO FIX for the slow issue. Once the drive starts to have problems then the drive MUST be replaced. Even ARCO / SELF-SCAN can't be considered a very reliable way to fix the drive. There is a "patch" that simply disable media scan for bad sectors and clear the re-lo list. This is to make the drive fast again in order to RECOVER THE DATA. This is NOT for drive re-use.


Alright, the term “fixed” wasn't the most appropriate, but that was kinda evident in that context : using a hard disk drive with even a few bad sectors for important data is always a bad idea, regardless of the brand, even without that specific issue on that range of WD drives, so I meant “fixed” in the sense “that particular issue can be dealt with if push comes to shove”.


Quote:
No hardware tool required and it's NOT that advanced ... It's quite simple honestly.


Most people (heck, even most general purpose computer professionals) don't know that hard drives have a firmware which can receive special commands, so even if it's relatively simple to do once you know how to do it, I would still say that this is an advanced procedure.


Quote:
Again if you have "pro" tools like PC-3000 DE when you clone a drive you can see what blocks are bad and what files belong to those blocks.


Yeah, I hope that pro tools (why do you use quotations marks here ? isn't this “professional” stuff in the strictest sense ?) can do everything that can be done in the most efficient and reliable way possible... but I currently don't have access to that kind of very expensive tools, so I do what I can do with what I can have ! :)


Quote:
Regarding cloning of bad drives if heads are dying it might be worth to go after the files you need first and only then attempt to clone the rest of the drive....


So my instincts were right (for once !) when I dealt with the 3TB one. But if everything is pretty much of the same importance, or it would be too tedious and time-consuming (a precious time when dealing with a failing HDD) to sort out what is absolutely crucial / important / useful / trivial, then it's probably best to do a full clone right away and hope for the best, like I did with the 2TB one.

What are the obvious symptoms of heads dying, as opposed to surface defects ?
For instance, here's a ddrescueview screenshot of a 1TB Hitachi HDD which was handed to me last summer. I tried to recover as much data as possible from it with software methods (ddrescue + R-Studio), and was quite succesful (luckily, it was only filled to about a quarter, so I got almost all the user data, only about 130 files were corrupted, according to ddru_ntfsfindbad, then as there were many duplicated files, which I identified with DoubleKiller, I managed to further repair more than 100 of them, the guy was very happy). Does such a pattern, with alternating stripes of good and bad areas, mean that one head was kaputt at that point ? At first I tried to copy everything, there were slowdowns but it was copying steadily ; then after about 200GB it started disconnecting, making frightening clicks, after a few power cycles it was writing again but very slowly, at which point I wondered if writing the image to a NTFS partition could be the cause as I had read in a ddrescue tutorial (I exposed the issue here) ; then I started all over again, strangely this time there were no slowdowns at the begining, but it started to have major hiccups earlier, around 160GB ; at some point I tried ddru_ntfsbitmap, which proved tremendously useful in a case like this (I should have done that at the begining), that's why large areas are non-tried beyond 250GB (those areas were marked as empty in the bitmap) ; I still had to give up after a while, as it had slowed down to a crawl and it would have taken hours to get 1MB.


Quote:
One VERY IMPORTANT consideration about the "slow issue" on WD drives and the "Pending BUG" on the Seagate ones is that on modern drives there is a BACKGROUND MEDIA SCAN meaning that you might have your drive idle doing nothing, your OS might not be requesting any data from the drive, might not be sending any command or in fact you might even get the SATA cable disconnected from the host and the drive itself while powered up might be scanning the surface for sectors that can't be properly read and be adding those sectors to the pending list. You don't even need to request to "read" or "verify" a problematic LBA, the drive might do that itself at firmware level unless you disable the correspondent "feature" by patching firmware .....


That answers a question I asked about the reallocated sector count from my ST2000DL003 which kept increasing even when letting it run idly for a few days – and that contradicts a common notion that bad sectors can only be reallocated after a failed write attempt.
Is this background scan reliable at least ? Or can it wrongly mark sectors as bad when in fact they're not ? (Meaning that the data they contained is lost.) The strange thing in this case is that surface scans with HD Sentinel still come out 100% clean...


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 Post subject: Re: Explaining Disk Check Results
PostPosted: January 8th, 2018, 23:33 
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Joined: November 22nd, 2017, 21:47
Posts: 309
Location: France
Regarding the HDDOracle guide you linked :

Quote:
Use your firmware tool and get a copy of all modules, place them on a safe place.


What do you call “firmware tool” here ? Hardware or software ?


Quote:
This is due to a problem similar with the Seagate F3 drives, when the drive gets "stuck" trying to re-locate sectors, or more specific, adding and managing the list of sectors that are "candidates" to be relocated. [...]
This operation is somehow correspondent to turning off relocation of Seagate F3 drives


Apparently that's what happened to my ST3000DM001 (the reallocated sector count and pending sector count were increasing constantly, and quite spectacularly, were around 10000 each last time I checked). Is there a similar, software-only procedure to turn that off on Seagate F3, or can it be done with a cheap adaptator, or does it require expensive hardware tools with those models ? (I have little hope that I can recover even one of the corrupted files, but that'd be worth a try, if only for educational purposes.)


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