bad sectors on a mybook WD usb drive
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From: Arno on 18 Feb 2010 18:15 sobriquet <dohduhdah(a)yahoo.com> wrote: > On 18 feb, 20:35, "Rod Speed" <rod.speed....(a)gmail.com> wrote: >> sobriquet wrote: >> > I've lost some data on a 2 tb WD mybook usb drive. When >> > I did a full scan, it found something like 3 mb in bad sectors. I assume that is 3 MB (which is 8'000'000'000 times more, "mb" is milli-bit, you want Mega-Byte). That is a lot. >> > However, when I reformatted the drive, somehow all bad sectors were >> > recovered. Apparently, there is some redundancy in diskspace, so it >> > can allocate some of that extra space to substitute for the bad >> > sectors on disk when it's just a small section of bad sectors. >> >> Yes, all modern hard drives have spare sectors >> that can be used as substitutes for bad sectors. >> >> > The disk is also able to pass the short drive test (in winDLG >> > under xp), that it used to fail, before I reformatted the drive. That is also normal. This "recovery" is only useful if the defects are not the fault of the drive. >> > Now I wonder if the fact that previously bad sectors have occurred and >> > I've lost data, is that increasing the likelyhood that this might happen again? >> >> Yes, that many bad sectors does indicate a problem with >> the drive or that the drive is running much too hot etc. >> >> > Is the drive less reliable in any way once a small >> > number of bad sectors have been identified Not necessarily. It depends on the reason. If it is the drives own fault, about 10 or more bad sectors are pretty bad. If it is extern influence (vibration, bad PSU,...) even a very, very large number like yours does not necessary say the drive is unreliable after (!) the external problem has been corrected. >> Yes, and 3MB is not a small number of bad sectors. >> >> > (even though the bad sectors are no longer visible after the drive has been >> > formatted again and other drivespace is substituted for the bad sectors)? >> >> Yes, it either indicates that the drive is dying, or that its running stinking hot etc. >> >> > ?Below is the original log from chdsk when the bad sectors were found: >> >> chkdsk isnt a very useful indication of the health of the drive. >> >> You really need a proper SMART report on the drive. >> >> That isnt necessarily that easy to get for free with an external drive. > Well, with winDLG, it does say the SMART status is OK for the device, > and I can get more detailed SMART info. The "smart status" is over-optimistic in most cases. > Here is a screenshot of the SMART info: > http://img11.imageshack.us/img11/74/wdmybook.jpg It is hard to say anything from this, as the raw values are missing. It looks as the defects were actually not replaced but really recoverd (attribute 5 is still at value 200) and nothing else is suspicuous. This looks like the sectors are fine, but something interferred with the write operation. How have you handled the drive? Moved it around or bumped it during operation? Used it with not too clean power? Used it on a surface that vibrated or was otherwise mechanically unstable? Arno -- Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno(a)wagner.name GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F ---- Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans
From: Franc Zabkar on 18 Feb 2010 23:55 On Thu, 18 Feb 2010 12:43:25 -0800 (PST), sobriquet <dohduhdah(a)yahoo.com> put finger to keyboard and composed: >Here is a screenshot of the SMART info: >http://img11.imageshack.us/img11/74/wdmybook.jpg IIUC, WD's temperature attribute assigns a normalised value of 100 to a temperature of 50C. A value of 89 would then suggest that the temperature is 61C. I could be wrong, though ... - Franc Zabkar -- Please remove one 'i' from my address when replying by email.
From: sobriquet on 19 Feb 2010 01:04 On 18 feb, 23:25, sobriquet <dohduh...(a)yahoo.com> wrote: > On 18 feb, 22:29, "Rod Speed" <rod.speed....(a)gmail.com> wrote: > > > > > > > sobriquet wrote > > > > Rod Speed <rod.speed....(a)gmail.com> wrote > > >> sobriquet wrote > > >>> I've lost some data on a 2 tb WD mybook usb drive. When > > >>> I did a full scan, it found something like 3 mb in bad sectors. > > >>> However, when I reformatted the drive, somehow all bad sectors were > > >>> recovered. Apparently, there is some redundancy in diskspace, so it > > >>> can allocate some of that extra space to substitute for the bad > > >>> sectors on disk when it's just a small section of bad sectors. > > >> Yes, all modern hard drives have spare sectors > > >> that can be used as substitutes for bad sectors. > > >>> The disk is also able to pass the short drive test (in winDLG > > >>> under xp), that it used to fail, before I reformatted the drive. > > >>> Now I wonder if the fact that previously bad sectors have occurred > > >>> and I've lost data, is that increasing the likelyhood that this might > > >>> happen again? > > >> Yes, that many bad sectors does indicate a problem with > > >> the drive or that the drive is running much too hot etc. > > >>> Is the drive less reliable in any way once a small > > >>> number of bad sectors have been identified > > >> Yes, and 3MB is not a small number of bad sectors. > > >>> (even though the bad sectors are no longer visible after the drive has > > >>> been formatted again and other drivespace is substituted for the bad sectors)? > > >> Yes, it either indicates that the drive is dying, or that its running stinking hot etc. > > >>> Below is the original log from chdsk when the bad sectors were found: > > >> chkdsk isnt a very useful indication of the health of the drive. > > >> You really need a proper SMART report on the drive. > > >> That isnt necessarily that easy to get for free with an external drive. > > > Well, with winDLG, it does say the SMART status is OK for the device, > > > That never means much, its the detailled values that matter. > > > > and I can get more detailed SMART info. > > > Here is a screenshot of the SMART info: > > >http://img11.imageshack.us/img11/74/wdmybook.jpg > > > It isnt at all clear what that actually means, particularly what the warranty field means. > > > And the reallocated sector entry and the temperature entry make no sense either. > > > The Everest SMART report is much more readable, > > but doesnt work with external drives in the free version. > > > smartclt from a linux bootable cd might, and HDSentinal might, but it isnt free. > > The version I've tried from HDSentinel wasn't up to date, but perhaps > the version (5.30) of Everest on demonoid will provide more detailed > SMART info on the drive. I'm busy with the drive now, but I'll soon > follow up on this with a screenshot of the Everest SMART info of the > drive. Screenshot of Everest SMART info of the same drive: http://img713.imageshack.us/img713/5343/everestje.jpg
From: sobriquet on 19 Feb 2010 08:05 On 19 feb, 00:15, Arno <m...(a)privacy.net> wrote: > sobriquet <dohduh...(a)yahoo.com> wrote: > > On 18 feb, 20:35, "Rod Speed" <rod.speed....(a)gmail.com> wrote: > >> sobriquet wrote: > >> > I've lost some data on a 2 tb WD mybook usb drive. When > >> > I did a full scan, it found something like 3 mb in bad sectors. > > I assume that is 3 MB (which is 8'000'000'000 times more, > "mb" is milli-bit, you want Mega-Byte). That is a lot. Millibit would make sense in this discussion (since computers don't deal with fractional bits), so obviously mb means megabyte, like tb means terrabyte. I'm sloppy with capitals sometimes, sorry. I thought 3 MB was not really that much in proportion to the total size of the drive (2 TB = 2 * 1024 * 1024 MB = 2097152 MB) > > >> > However, when I reformatted the drive, somehow all bad sectors were > >> > recovered. Apparently, there is some redundancy in diskspace, so it > >> > can allocate some of that extra space to substitute for the bad > >> > sectors on disk when it's just a small section of bad sectors. > > >> Yes, all modern hard drives have spare sectors > >> that can be used as substitutes for bad sectors. > > >> > The disk is also able to pass the short drive test (in winDLG > >> > under xp), that it used to fail, before I reformatted the drive. > > That is also normal. This "recovery" is only useful > if the defects are not the fault of the drive. > > >> > Now I wonder if the fact that previously bad sectors have occurred and > >> > I've lost data, is that increasing the likelyhood that this might happen again? > > >> Yes, that many bad sectors does indicate a problem with > >> the drive or that the drive is running much too hot etc. > > >> > Is the drive less reliable in any way once a small > >> > number of bad sectors have been identified > > Not necessarily. It depends on the reason. If it is the drives > own fault, about 10 or more bad sectors are pretty bad. > If it is extern influence (vibration, bad PSU,...) even > a very, very large number like yours does not necessary > say the drive is unreliable after (!) the external problem > has been corrected. > How much redundant space does a typical 2 TB drive have to replace bad sectors? The drive was in operation on an uneven surface and perhaps it moved around or bumped slightly during operation. I hope solid state disks will become more affordable soon, as they seem more resilient to minor shocks. > > > > > >> Yes, and 3MB is not a small number of bad sectors. > > >> > (even though the bad sectors are no longer visible after the drive has been > >> > formatted again and other drivespace is substituted for the bad sectors)? > > >> Yes, it either indicates that the drive is dying, or that its running stinking hot etc. > > >> > ?Below is the original log from chdsk when the bad sectors were found: > > >> chkdsk isnt a very useful indication of the health of the drive. > > >> You really need a proper SMART report on the drive. > > >> That isnt necessarily that easy to get for free with an external drive.. > > Well, with winDLG, it does say the SMART status is OK for the device, > > and I can get more detailed SMART info. > > The "smart status" is over-optimistic in most cases. > > > Here is a screenshot of the SMART info: > >http://img11.imageshack.us/img11/74/wdmybook.jpg > > It is hard to say anything from this, as the raw values > are missing. It looks as the defects were actually not > replaced but really recoverd (attribute 5 is still > at value 200) and nothing else is suspicuous. > This looks like the sectors are fine, but something > interferred with the write operation. I have another screenshot that also shows the raw values. http://img713.imageshack.us/img713/5343/everestje.jpg > > How have you handled the drive? Moved it around > or bumped it during operation? Used it with not too > clean power? Used it on a surface that vibrated or > was otherwise mechanically unstable? Well, in a typical situation, I might have the drive on the desk and then being somewhat absent minded, I might be drumming along with some music with my hands on the desk a bit too enthusiastically, which might make the disk vibrate too much. I dunno how sensitive these drives are and how much of a shock might pose a serious problem during reading from or writing to the drive. > > Arno > -- > Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: a...(a)wagner.name > GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F > ---- > Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans
From: Arno on 19 Feb 2010 09:35
sobriquet <dohduhdah(a)yahoo.com> wrote: > On 19 feb, 00:15, Arno <m...(a)privacy.net> wrote: >> sobriquet <dohduh...(a)yahoo.com> wrote: >> > On 18 feb, 20:35, "Rod Speed" <rod.speed....(a)gmail.com> wrote: >> >> sobriquet wrote: >> >> > I've lost some data on a 2 tb WD mybook usb drive. When >> >> > I did a full scan, it found something like 3 mb in bad sectors. >> >> I assume that is 3 MB (which is 8'000'000'000 times more, >> "mb" is milli-bit, you want Mega-Byte). That is a lot. > Millibit would make sense in this discussion (since computers don't > deal with fractional bits), so obviously mb means megabyte, like tb > means terrabyte. I'm sloppy with capitals sometimes, sorry. The "m" is not that bad, but "b" is bit while "B" is Byte. > I thought 3 MB was not really that much in proportion to the total > size of the drive (2 TB = 2 * 1024 * 1024 MB = 2097152 MB) Defect sectors should be counted in number per device. 3MB is about 6000 defective secotrs, which is a massive number. Typically drives are highly suspicuous from 10 defectives onwards and I have only seen one drive so far with more than 50 defects that was not dying (it got 200 defects in a day and then never any additional ones, I suspect vibration from some work being done next to the computer). [...] >> >> > Is the drive less reliable in any way once a small >> >> > number of bad sectors have been identified >> >> Not necessarily. It depends on the reason. If it is the drives >> own fault, about 10 or more bad sectors are pretty bad. >> If it is extern influence (vibration, bad PSU,...) even >> a very, very large number like yours does not necessary >> say the drive is unreliable after (!) the external problem >> has been corrected. >> > How much redundant space does a typical 2 TB drive have to replace bad > sectors? > The drive was in operation on an uneven surface and perhaps it moved > around or bumped slightly > during operation. > I hope solid state disks will become more affordable soon, as they > seem more resilient to minor shocks. The problem is less the reallocation space, and more that for each defective sector there is a very real chance the data stored in it is gone. If you do a verify read that risk is mostly eleminated if the reason is not a defective drive, but an environmental problem. [...] >> > Well, with winDLG, it does say the SMART status is OK for the device, >> > and I can get more detailed SMART info. >> >> The "smart status" is over-optimistic in most cases. >> >> > Here is a screenshot of the SMART info: >> >http://img11.imageshack.us/img11/74/wdmybook.jpg >> >> It is hard to say anything from this, as the raw values >> are missing. It looks as the defects were actually not >> replaced but really recoverd (attribute 5 is still >> at value 200) and nothing else is suspicuous. >> This looks like the sectors are fine, but something >> interferred with the write operation. > I have another screenshot that also shows the raw values. > http://img713.imageshack.us/img713/5343/everestje.jpg Except for the temperature, the drive looks perfectly healty. The temperature is 63C (if the encoding is the same as on other WD drives) and 63C is deep into HDD killer territory. More than 50C is reason for real concern and typically above the maximum allowed temperature. From 65-75C or so, the mechanics and electronics starts to fail (non-permanently, but ageing very fast, like beging dead from old age within weeks-months), so that is possibly were your defects came from: You got the disk so hot it stopped working right. You need to bring donwn the temperature. The non-perfect scores on the "Worst" vlaue for C5 and C8 indicate, there was a serious problem but it is gone at the moment. >> How have you handled the drive? Moved it around >> or bumped it during operation? Used it with not too >> clean power? Used it on a surface that vibrated or >> was otherwise mechanically unstable? > Well, in a typical situation, I might have the drive on the desk and > then being somewhat absent minded, I might be drumming along with some > music with my hands on the desk a bit too enthusiastically, which > might make the disk vibrate too much. > I dunno how sensitive these drives are and how much of a shock might > pose a serious problem during reading from or writing to the drive. Maybe. Lound sounds can cause problems. Here is an enlightening video demonstrating the effect: http://www.youtube.com/watch?v=tDacjrSCeq4 This can also cause write defects, were the data is unreadable (i.e. you have data loss) but the sector is again fine after an overwrite. Arno -- Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno(a)wagner.name GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F ---- Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans |