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#1
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zeroing/data-filling fixes hard disk?
Can zeroing a hard drive fix previously unusable blocks? It makes no
intuitive sense to me how putting certain data on a drive could affect the readability of any of its sectors, but I seem to be seeing that. My hard disk drive *seemed* to be irretrievably messed up and now it seems to be claiming it's fine after I've done some combination of zero-filling it and data-filling it. All tests done with the drive offline. I've never seen such a thing before. Is my drive really fixed? I actually had heard before that zero-filling a hard-drive could help a problem drive work properly again, but that seems to make no sense, but in fact I now seem to be seeing it. I'm running Linux with this drive. I discovered the problem when suddenly I noticed strange "I/O Error" messages when I was just doing ordinary things in directories. I looked into the logs and found disturbing low-level sector access problems. I ran the linux "badblocks" program in read-only mode and I then saw the same errors popping up on my system's console. Immediately after this, the machine became unbootable. I figured the HD was toast. Anyway, I got all my data off as best I could and just completed various "wipes" of the disk, some zero-filling and some data-filling (0xAA's and such, done in pieces because the wipe was taking forever once it hit bad sectors in the early part of the drive, so I averted the sections I knew had bad stuff in them to make the wipe go faster). And now? My drive is magically reporting no problems, I have the test running now and I'm seeing no console messages at all and I've already passed the part of the drive that was producing reams and reams of these messages previously. Does this make any possible sense? |
#2
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On Thu, 11 Dec 2003 05:54:38 GMT
"wlcna" wrote: Can zeroing a hard drive fix previously unusable blocks? It makes no intuitive sense to me how putting certain data on a drive could affect the readability of any of its sectors, but I seem to be seeing that. My hard disk drive *seemed* to be irretrievably messed up and now it seems to be claiming it's fine after I've done some combination of zero-filling it and data-filling it. All tests done with the drive offline. I've never seen such a thing before. Is my drive really fixed? I actually had heard before that zero-filling a hard-drive could help a problem drive work properly again, but that seems to make no sense, but in fact I now seem to be seeing it. I'm running Linux with this drive. I discovered the problem when suddenly I noticed strange "I/O Error" messages when I was just doing ordinary things in directories. I looked into the logs and found disturbing low-level sector access problems. I ran the linux "badblocks" program in read-only mode and I then saw the same errors popping up on my system's console. Immediately after this, the machine became unbootable. I figured the HD was toast. Anyway, I got all my data off as best I could and just completed various"wipes" of the disk, some zero-filling and some data-filling (0xAA's and such, done in pieces because the wipe was taking forever once it hit bad sectors in the early part of the drive, so I averted the sections I knew had bad stuff in them to make the wipe go faster). And now? My drive is magically reporting no problems, I have the test running now and I'm seeing no console messages at all and I've already passed the part of the drive that was producing reams and reams of these messages previously. Does this make any possible sense? It's called "sparing". Any contemporary drive has a number of spare sectors and the logic to use them--when it is reading and it finds a bad sector it can't do a lot about it except complain because it doesn't have a good copy of the data, but when it's writing and it encounters a bad sector it just marks it bad and swaps in one of the spares. So your zero-fill wrote to all normally accessible sectors and the drive could then swap out all the bad ones. -- -- --John Reply to jclarke at ae tee tee global dot net (was jclarke at eye bee em dot net) |
#3
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"wlcna" wrote in message y.com Can zeroing a hard drive fix previously unusable blocks? It makes no intuitive sense to me how putting certain data on a drive could affect the readability of any of its sectors, but I seem to be seeing that. My hard disk drive *seemed* to be irretrievably messed up and now it seems to be claiming it's fine after I've done some combination of zero-filling it and data-filling it. All tests done with the drive offline. I've never seen such a thing before. Is my drive really fixed? I actually had heard before that zero-filling a hard-drive could help a problem drive work properly again, but that seems to make no sense, but in fact I now seem to be seeing it. I'm running Linux with this drive. I discovered the problem when suddenly I noticed strange "I/O Error" messages when I was just doing ordinary things in directories. I looked into the logs and found disturbing low-level sector access problems. I ran the linux "badblocks" program in read-only mode and I then saw the same errors popping up on my system's console. Immediately after this, the machine became unbootable. I figured the HD was toast. Anyway, I got all my data off as best I could and just completed various "wipes" of the disk, some zero-filling and some data-filling (0xAA's and such, done in pieces because the wipe was taking forever once it hit bad sectors in the early part of the drive, so I averted the sections I knew had bad stuff in them to make the wipe go faster). And now? My drive is magically reporting no problems, I have the test running now and I'm seeing no console messages at all and I've already passed the part of the drive that was producing reams and reams of these messages previously. Does this make any possible sense? No. Not with those problem areas skipped (not been written over). |
#4
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"J.Clarke" wrote in message d On Thu, 11 Dec 2003 05:54:38 GMT "wlcna" wrote: Can zeroing a hard drive fix previously unusable blocks? It makes no intuitive sense to me how putting certain data on a drive could affect the readability of any of its sectors, but I seem to be seeing that. My hard disk drive *seemed* to be irretrievably messed up and now it seems to be claiming it's fine after I've done some combination of zero-filling it and data-filling it. All tests done with the drive offline. I've never seen such a thing before. Is my drive really fixed? I actually had heard before that zero-filling a hard-drive could help a problem drive work properly again, but that seems to make no sense, but in fact I now seem to be seeing it. I'm running Linux with this drive. I discovered the problem when suddenly I noticed strange "I/O Error" messages when I was just doing ordinary things in directories. I looked into the logs and found disturbing low-level sector access problems. I ran the linux "badblocks" program in read-only mode and I then saw the same errors popping up on my system's console. Immediately after this, the machine became unbootable. I figured the HD was toast. Anyway, I got all my data off as best I could and just completed various"wipes" of the disk, some zero-filling and some data-filling (0xAA's and such, done in pieces because the wipe was taking forever once it hit bad sectors in the early part of the drive, so I averted the sections I knew had bad stuff in them to make the wipe go faster). And now? My drive is magically reporting no problems, I have the test running now and I'm seeing no console messages at all and I've already passed the part of the drive that was producing reams and reams of these messages previously. Does this make any possible sense? It's called "sparing". Any contemporary drive has a number of spare sectors and the logic to use them -- when it is reading and it finds a bad sector it can't do a lot about it except complain because it doesn't have a good copy of the data, This is where the sector is marked a 'bad sector candidate' in the drive's internal administration. but when it's writing and it encounters a bad sector it just marks it bad You've got that mangled entirely. There is no way a drive can detect a bad data sector on a write unless it knows beforehand from it's own internal administration. and swaps in one of the spares. If necessary. The drive will test the sector and if it turns out good it will reuse that sector. So your zero-fill wrote to all normally accessible sectors and the drive could then swap out all the bad ones. Problem is: he said that he avoided some areas that contained the bad sectors to speed things up. -- |
#5
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"J.Clarke" wrote in message
d... It's called "sparing". Any contemporary drive has a number of spare sectors and the logic to use them--when it is reading and it finds a bad sector it can't do a lot about it except complain because it doesn't have a good copy of the data, but when it's writing and it encounters a bad sector it just marks it bad and swaps in one of the spares. So your zero-fill wrote to all normally accessible sectors and the drive could then swap out all the bad ones. Thanks much for this clarification. That does make sense now. I've always thought of disks as tracks and cylinders that are contiguous, this "fix up" idea is new to me but makes sense. I would wonder how effective it would be though, because for example in my case the problem seemed to be affecting more and more sectors all the time. Being that a disk *is* a thing with tracks, cylinders and such, isn't it true that when some go bad, they may tend to start going bad in a certain unison over time? Anyway, just curious, but thanks for this information. |
#6
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"Folkert Rienstra" wrote in message
... "J.Clarke" wrote in message d On Thu, 11 Dec 2003 05:54:38 GMT "wlcna" wrote: So your zero-fill wrote to all normally accessible sectors and the drive could then swap out all the bad ones. Problem is: he said that he avoided some areas that contained the bad sectors to speed things up. Here's one point that may clarify things: I was doing initially read-only tests and then later write-based tests. The write-based tests are the ones that were occurring when I stopped seeing the console messages about failures. Now I may have formulated my plan for skipping the bad sectors while doing the read tests, but at the end of the whole process, I did use a write-based test on the whole disk, and that was when I saw what I've mentioned, no low-level errors appearing on the console. I did not realize there was this read/write error traceability difference. Perhaps if I had done a write-based test initially, I wouldn't have seen any messages b/c according to you the drive can't tell anything about a sector being bad at write time. It seems that the lack of errors I was seeing may not even be meaningful according to what you've said, since at write time the drive can't tell if it's a bad sector or not. I stopped the test before it finished doing the second part of the test, going from the beginning again and actually comparing the values it wrote (linux badblocks writes in one long sweep then only tests in a later sweep). I think I tried a simple read-only badblocks test and that seemed to be working, not sure about that though, I was really getting sick of the drive at that point, and it's back in a box now, hopefully never to be seen by me again. |
#7
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On Sat, 13 Dec 2003 06:36:08 GMT
"wlcna" wrote: "J.Clarke" wrote in message d... It's called "sparing". Any contemporary drive has a number of spare sectors and the logic to use them--when it is reading and it finds a bad sector it can't do a lot about it except complain because it doesn't have a good copy of the data, but when it's writing and it encounters a bad sector it just marks it bad and swaps in one of the spares. So your zero-fill wrote to all normally accessible sectors and the drive could then swap out all the bad ones. Thanks much for this clarification. That does make sense now. I've always thought of disks as tracks and cylinders that are contiguous, this"fix up" idea is new to me but makes sense. I would wonder how effective it would be though, because for example in my case the problem seemed to be affecting more and more sectors all the time. Being that a disk *is* a thing with tracks, cylinders and such, isn't it true that when some go bad, they may tend to start going bad in a certain unison over time? Generally speaking, and ignoring sparing, a drive will have a few bad sectors when it comes from the factory. A few more may show up in the first few weeks of operation. Then others will show up very rarely. Eventually the drive dies for whatever reason--one of they ways a drive may die is to show a rapidly increasing number of bad sectors. When this happens sparing may mask the problem for a while, but eventually it surfaces. When you have a drive showing a rapidly increasing number of bad sectors it's generally wise to consider it to be on the verge of failure and back it up before dinking with it further. Even though writing all sectors allows the bad sectors to be swapped out eventually all the spares will get used up. Anyway, just curious, but thanks for this information. -- -- --John Reply to jclarke at ae tee tee global dot net (was jclarke at eye bee em dot net) |
#8
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"wlcna" wrote in message y.com
"Folkert Rienstra" wrote in message ... "J.Clarke" wrote in message d On Thu, 11 Dec 2003 05:54:38 GMT "wlcna" wrote: So your zero-fill wrote to all normally accessible sectors and the drive could then swap out all the bad ones. Problem is: he said that he avoided some areas that contained the bad sectors to speed things up. Here's one point that may clarify things: I was doing initially read-only tests and then later write-based tests. The write-based tests are the ones that were occurring when I stopped seeing the console messages about failures. Now I may have formulated my plan for skipping the bad sectors while doing the read tests, but at the end of the whole process, I did use a write-based test on the whole disk, OK, that makes a lot more sense. and that was when I saw what I've mentioned, no low-level errors appearing on the console. As expected. I did not realize there was this read/write error traceability difference. Data errors are only detected on reads. Writes are not checked. Write errors e.g., may occur when the drive is unable to find the sector. There are 2 possibilities: the error is soft (retries succeed eventually) and the sector is reassigned on the read or the error is hard (unrecover- able) and the sector is indicated as a 'candidate bad sector'. The 'can- didate bad sector' can be reassigned on the next write to that sector. Perhaps if I had done a write-based test initially, I wouldn't have seen any messages b/c according to you the drive can't tell anything about a sector being bad at write time. Correct. That would require a write-check (which is very slow). It seems that the lack of errors I was seeing may not even be meaningful according to what you've said, since at write time the drive can't tell if it's a bad sector or not. It certainly can from it's internal administration, except that that info is gathered at read time. Writes to a sector go unchecked except when it is internally registered as a 'bad sector candidate'. I stopped the test before it finished doing the second part of the test, going from the beginning again and actually comparing the values it wrote (linux badblocks writes in one long sweep then only tests in a later sweep). I think I tried a simple read-only badblocks test and that seemed to be working, not sure about that though, I was really getting sick of the drive at that point, and it's back in a box now, hopefully never to be seen by me again. |
#9
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"wlcna" wrote in message y.com "J.Clarke" wrote in message d... It's called "sparing". Any contemporary drive has a number of spare sectors and the logic to use them--when it is reading and it finds a bad sector it can't do a lot about it except complain because it doesn't have a good copy of the data, but when it's writing and it encounters a bad sector it just marks it bad and swaps in one of the spares. So your zero-fill wrote to all normally accessible sectors and the drive could then swap out all the bad ones. Thanks much for this clarification. That does make sense now. I've always thought of disks as tracks and cylinders that are contiguous, It still was, once, when the spares resided in the same track or cylinder and the remaining track was reordered (called a pushdown) so that the sequential order was still maintained. That was a bit expensive and also stood in the way of making drives faster so on current drive spares usually are at the end of the medium now. This means that sector A and sector A+1 can be in very different places after a bad sector reassigned. Some drives can be low level formatted in such a way that the sequential order of *all* sectors is again restored, like when it came from the factory. this "fix up" idea is new to me but makes sense. I would wonder how effective it would be though, because for example in my case the problem seemed to be affecting more and more sectors all the time. It does in situations where external problems cause the bad sectors. After taking care of the external causes the drive can be back to new. Being that a disk *is* a thing with tracks, cylinders and such, isn't it true that when some go bad, they may tend to start going bad in a certain unison over time? I fail to see what that has to do with "tracks, cylinders and such". Anyway, just curious, but thanks for this information. |
#10
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Some drives can be commanded to do read-after-write check for a few
power-ups (Maxtor, others?). The vendor's utility may employ this feature. "Folkert Rienstra" wrote in message ... "wlcna" wrote in message y.com I did not realize there was this read/write error traceability difference. Data errors are only detected on reads. Writes are not checked. Write errors e.g., may occur when the drive is unable to find the sector. There are 2 possibilities: the error is soft (retries succeed eventually) and the sector is reassigned on the read or the error is hard (unrecover- able) and the sector is indicated as a 'candidate bad sector'. The 'can- didate bad sector' can be reassigned on the next write to that sector. Perhaps if I had done a write-based test initially, I wouldn't have seen any messages b/c according to you the drive can't tell anything about a sector being bad at write time. Correct. That would require a write-check (which is very slow). |
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