Need help with "reallocated sector count"?
in [Storage]
|
Prev: INT13/02h Read error (AX=0100, DL=80) trying xp installation in SATA
Next: Need to create a CDFS partition on a USB key
From: kimiraikkonen on 14 Nov 2007 12:23 On Nov 14, 12:55 pm, Arno Wagner <m...(a)privacy.net> wrote: > Previously kimiraikkonen <kimiraikkone...(a)gmail.com> wrote: > > Arno, Rod (no quatiton mark :-) ), Franc, > > Thanks you for following this topic and keeping replying. > > So, as overall when you looked at SMART values, i want to summarize > > what i got in that topic? > > 1- There are 98 reallocated bad sectors but there's no unallocated as > > a threat of data loss? Right? > > The 98 sectors have been moved out of the way. Not risk from them. So, they were containing data before they've got reallocated. Right? > > 2-ID Attribute Description Threshold Value Worst Data Status > > 05 Reallocated Sector Count 36 98 98 98 OK: Value is normal > > That means there are 98 reallocated sectors, but still couldn't > > completely understand for Seagate what "threshold - 36" means? It > > shouldn't be percantage, does it mean that i'm allowed to allocate > > 100-36 = 64 bad ones? (frustrating) > > You have bad sector number x. This inceases on more bad sectors > found. By some obscure procedure that gives value y. This decreses > with more bad secors found. A first hypothesist is that y decreses > by 2 for every 98 bad sectors. The asumption is that the > initial value was 100. Then you have threshold value z. > If y ever reaches or falls below z, then you get a bad SMART status > for the disk. Very frustrating but good sample if it's straight forward true. Manufacturer have to explain their raw value and Smart calculations than guessing. > The current speculation is that in your particular case x and y > have the same numerical value, purely by accident. > > > 3- The other SMART values are fine as stated by many programs. Right? > > Looked that way. > > > 4- A "reallocated sector count" shows the amount of reallocated / > > replaced sectors silently while the drive is operating. When the drive > > has a problem with sector, first it tries to replace that sectors with > > a "spare" sector thus a "reallocated sector" statistic is updated. > > The reallocation count will increase on any successful > realocation. How much sector will my drive be allowed to reallocate? (eg: What about for a modern 40gb drive ? ) > Reallocation can happen later. If it was unsuccesful so far, you > get a "pending sector". As son as it has been reallocated, > the pending secor attribut is decreased again. > > > If the sector is completely unreadable or unreallocatable, you see it > > as "bad" marked in surface scan tools like Seatools. Did i understand > > correct? > > Yes. That's why the full / surface scan utilities are there. They report "bad" , really "bad" sectors which can't be allocated by firmware of HDD. Right? > > 5- Though a drive has "reallocated sectors", if it can read every data > > (checking with several disk reading utilites), it doesn't have a > > unallocatable / unfixable bad sectos which are the reasons of real > > data loss. > > The reallocated sectros are recognized _and_ corrected problems. > These sectors will not cause problems in the future. Other > sectors may go bad, but if a complete surface scan does not > show any, all data is in sectors that are fine or at least look > like it. In rare cases a sector can work with some data, but be > defect with other data. Very rare with today's disks, due to > heavy use of error correcting codes. > > You still may want to do a complete surface scan regularly, > so that the disk can recognize sectors slowly going bad > in time and can rescue the data in them. I run such a test > every 14 days automatically, but once every 1-2 months should > do fine. You can make that a part of your standard backup > procedure. I usually do it if i record important data. But still "none" bad sectors have been reported by surface scan of Seatools. So, can i say i don't have any bad sectors present at the moment? > > Those 5 questions are the ones i see answered them clearly. > > Again, thank you for following and helping. Very helpful... > > You are welcome. > > Arno Thanks.
From: Rod Speed on 14 Nov 2007 13:40 kimiraikkonen <kimiraikkonen85(a)gmail.com> wrote > Arno Wagner <m...(a)privacy.net> wrote >> kimiraikkonen <kimiraikkone...(a)gmail.com> wrote >>> Arno, Rod (no quatiton mark :-) ), Franc, >>> Thanks you for following this topic and keeping replying. >>> So, as overall when you looked at SMART values, i want to summarize >>> what i got in that topic? >>> 1- There are 98 reallocated bad sectors but there's no unallocated >>> as a threat of data loss? Right? >> The 98 sectors have been moved out of the way. Not risk from them. > So, they were containing data before they've got reallocated. Right? Yes, but were reallocated when an attempt was made to write to them, or when they were marginal and could be read so the data could be moved to the replacement sector. >>> 2-ID Attribute Description Threshold Value Worst >>> Data Status 05 Reallocated Sector Count 36 >>> 98 98 98 OK: Value is normal That means there are 98 >>> reallocated sectors, but still couldn't >>> completely understand for Seagate what "threshold - 36" means? It >>> shouldn't be percantage, does it mean that i'm allowed to allocate >>> 100-36 = 64 bad ones? (frustrating) >> You have bad sector number x. This inceases on more bad sectors >> found. By some obscure procedure that gives value y. This decreses >> with more bad secors found. A first hypothesist is that y decreses >> by 2 for every 98 bad sectors. The asumption is that the >> initial value was 100. Then you have threshold value z. >> If y ever reaches or falls below z, then you get a bad SMART status for the disk. Thats rather comprehensively mangled and you cant be sure exactly what that drive does with those values. > Very frustrating but good sample if it's straight forward true. > Manufacturer have to explain their raw value and Smart calculations And they almost never do explain the smart calculations. > than guessing. They never guess. Presumably you mean the end users shouldnt have to guess. >> The current speculation is that in your particular case x >> and y have the same numerical value, purely by accident. >>> 3- The other SMART values are fine as stated by many programs. Right? >> Looked that way. >>> 4- A "reallocated sector count" shows the amount of reallocated / >>> replaced sectors silently while the drive is operating. When the drive >>> has a problem with sector, first it tries to replace that sectors with >>> a "spare" sector thus a "reallocated sector" statistic is updated. >> The reallocation count will increase on any successful realocation. > How much sector will my drive be allowed to reallocate? Thats never an absolute and most manufacturers dont say how many spares there are. > (eg: What about for a modern 40gb drive ? ) Typically thousands. >> Reallocation can happen later. If it was unsuccesful so >> far, you get a "pending sector". As son as it has been >> reallocated, the pending secor attribut is decreased again. >>> If the sector is completely unreadable or unreallocatable, you see it as >>> "bad" marked in surface scan tools like Seatools. Did i understand correct? >> Yes. > That's why the full / surface scan utilities are there. Nope, they're there before they were there before SMART ever showed up. > They report "bad" , really "bad" sectors which > can't be allocated by firmware of HDD. Right? Nope, they are mostly reporting bads that the drive currently chooses not to reallocate, because the user needs to be allowed to get the data out of those sectors if they havent been backed up properly. The only time you see bads continue to be reported by those utes after every sector on the drive has been WRITTEN to, is when there arent any more spare sectors available. >>> 5- Though a drive has "reallocated sectors", if it can read every data >>> (checking with several disk reading utilites), it doesn't have a unallocatable >>> / unfixable bad sectos which are the reasons of real data loss. >> The reallocated sectros are recognized _and_ corrected problems. >> These sectors will not cause problems in the future. Other >> sectors may go bad, but if a complete surface scan does not >> show any, all data is in sectors that are fine or at least look >> like it. In rare cases a sector can work with some data, but be >> defect with other data. Very rare with today's disks, due to >> heavy use of error correcting codes. >> You still may want to do a complete surface scan regularly, >> so that the disk can recognize sectors slowly going bad >> in time and can rescue the data in them. And he means the SMART complete surface scan, not the OS level one. >> I run such a test every 14 days automatically, but once every 1-2 months >> should do fine. You can make that a part of your standard backup procedure. > I usually do it if i record important data. It makes a lot more sense to backup properly instead, because the data can go missing for other reasons like theft, fire etc. > But still "none" bad sectors have been reported by surface scan of Seatools. > So, can i say i don't have any bad sectors present at the moment? Correct, they have all been successfully reallocated and you can see that from the SMART report, no pending or unreallocatable sectors. >>> Those 5 questions are the ones i see answered them clearly. >>> Again, thank you for following and helping. Very helpful... >> You are welcome.
From: Franc Zabkar on 14 Nov 2007 15:24 On 13 Nov 2007 07:34:38 GMT, Arno Wagner <me(a)privacy.net> put finger to keyboard and composed: >I once had a Maxtor (in a cluster of compute servers) >that was incredible slow and has about 1100 reallocated sectors. >This thing was dying pretty fast (had been dropped and it >took some weeks to develop problems). The thing was that the >SMART status still read good, i.e. above the threshold. >At that time I started monitoring the raw reallocated sector >count and installed email notification on changes of that.. > >Some vendors are extremely optimisticc with regard to SMART >thresholds. Kind of makes the SMART status alone pretty >worthless. No wonder so many people are asking in this group >for help interpreting SMART data. > >Arno I retired my drive after it started growing bad sectors on a daily basis. The last bad sector couldn't be reallocated and showed up as an unreadable software file. Sure the drive could have been "fixed" by replacing the file and allowing SMART to reallocate the affected sector, but I didn't want to have to do this on a regular basis. So I can understand why some people replace a drive at the first hint of trouble. Twenty years ago I was servicing the old Control Data storage module drives with removable disc packs. If you started to see read errors, you could clean the disc heads with alcohol to remove any oxide buildup on the head pads. This contamination was the result of minor head-to-disc contact and affected the aerodynamics of the head. Once you started to see this problem, then you could very quickly end up with a head crash. - Franc Zabkar -- Please remove one 'i' from my address when replying by email.
From: Rod Speed on 14 Nov 2007 15:56 Franc Zabkar <fzabkar(a)iinternode.on.net> wrote: > On 13 Nov 2007 07:34:38 GMT, Arno Wagner <me(a)privacy.net> put finger > to keyboard and composed: > >> I once had a Maxtor (in a cluster of compute servers) >> that was incredible slow and has about 1100 reallocated sectors. >> This thing was dying pretty fast (had been dropped and it >> took some weeks to develop problems). The thing was that the >> SMART status still read good, i.e. above the threshold. >> At that time I started monitoring the raw reallocated sector >> count and installed email notification on changes of that.. >> >> Some vendors are extremely optimisticc with regard to SMART >> thresholds. Kind of makes the SMART status alone pretty >> worthless. No wonder so many people are asking in this group >> for help interpreting SMART data. >> >> Arno > > I retired my drive after it started growing bad sectors on a daily > basis. The last bad sector couldn't be reallocated and showed up as an > unreadable software file. Sure the drive could have been "fixed" by > replacing the file and allowing SMART to reallocate the affected > sector, but I didn't want to have to do this on a regular basis. So I > can understand why some people replace a drive at the first hint of > trouble. > > Twenty years ago I was servicing the old Control Data storage module > drives with removable disc packs. If you started to see read errors, > you could clean the disc heads with alcohol to remove any oxide > buildup on the head pads. This contamination was the result of minor > head-to-disc contact and affected the aerodynamics of the head. Once > you started to see this problem, then you could very quickly end up > with a head crash. And modern hard drives dont have the particular problem.
From: Franc Zabkar on 14 Nov 2007 16:04
On Wed, 14 Nov 2007 09:23:45 -0800, kimiraikkonen <kimiraikkonen85(a)gmail.com> put finger to keyboard and composed: >On Nov 14, 12:55 pm, Arno Wagner <m...(a)privacy.net> wrote: >> Previously kimiraikkonen <kimiraikkone...(a)gmail.com> wrote: >> > Arno, Rod (no quatiton mark :-) ), Franc, >> > Thanks you for following this topic and keeping replying. >> > So, as overall when you looked at SMART values, i want to summarize >> > what i got in that topic? >> > 1- There are 98 reallocated bad sectors but there's no unallocated as >> > a threat of data loss? Right? >> >> The 98 sectors have been moved out of the way. Not risk from them. > >So, they were containing data before they've got reallocated. Right? Probably, although you could have encountered some bad sectors from an unused portion of the disc by running Scandisk with a thorough surface scan. <snip> >How much sector will my drive be allowed to reallocate? (eg: What >about for a modern 40gb drive ? ) I posted some stats for my 13GB Seagate HD. If my assumptions are correct, then each percentage point reflects a loss of approximately 40 sectors. In my case that means that my drive can reallocate 2560 sectors before it drops below the threshold, after which it should return a bad SMART status. If I were you I would backup and retire your drive. Once it starts to develop bad sectors, then the numbers can only grow. You need to ask yourself how important your data are. >That's why the full / surface scan utilities are there. They report >"bad" , really "bad" sectors which can't be allocated by firmware of >HDD. Right? AFAIK, all bad sectors can be reallocated, if enough spares are available. The problem in this particular case is that the drive will not reallocate an uncorrectable bad sector until it is sure that the OS no longer wants the data contained within it. The way that the OS signals that the data in this sector are no longer of any consequence is by writing to it. As soon as the drive is asked to write to this bad sector, it reallocates a spare and writes the new data to it instead. In my case I have had a "pending" sector for almost the entire life of the drive. This is because I ran Scandisk with a thorough surface scan after FDISKing and formatting my drive. Scandisk found one bad sector and marked is as such in the FAT. Hence the OS has avoided writing to it ever since and the "pending" status has remained. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |