HDD problems causing Kernel panics in Linux/Debian?
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From: Bob on 8 Mar 2010 10:00 On 03/07/2010 02:54 PM, Rod Speed wrote: > Yousuf Khan wrote >> Pascal Hambourg wrote >>> Rod Speed wrote >>>> Pascal Hambourg wrote > >>>>> Aren't pending sectors sectors waiting to be remapped because of read errors ? > >>>> Thats not the same thing as unreadable sectors. > >>> Aren't pending sectors unreadable, because of read errors ? > >> Pending sectors are still readable, > > Some of them are unreadable, just not all of them are. > >> but they are weak when it comes time to write to them. So they are pending remapping during the next write to them. > > Even unreadable sectors are marked as pending until the write, so you > can attempt to get what data is in them before the write/reallocate. > More importantly, it's so that you will continue to get an I/O error when you try to read the file that contains that sector. It would be a Very Bad Thing (tm) if you got whatever junk was in the reallocated sector (remember, the drive could not recover the original data) with no error indication. Even if the bad sector is part of your file system's free space or is otherwise irrelevant, the drive has no way to know that. The drive has to keep the bad sector visible to the OS until you direct a write there, at which point the original content is no longer relevant. -- Bob Nichols AT comcast.net I am "RNichols42"
From: Rod Speed on 8 Mar 2010 12:24 Bob wrote > Rod Speed wrote >> Yousuf Khan wrote >>> Pascal Hambourg wrote >>>> Rod Speed wrote >>>>> Pascal Hambourg wrote >>>>>> Aren't pending sectors sectors waiting to be remapped because of read errors ? >>>>> Thats not the same thing as unreadable sectors. >>>> Aren't pending sectors unreadable, because of read errors ? >>> Pending sectors are still readable, >> Some of them are unreadable, just not all of them are. >>> but they are weak when it comes time to write to them. So they are pending remapping during the next write to them. >> Even unreadable sectors are marked as pending until the write, so you >> can attempt to get what data is in them before the write/reallocate. > More importantly, it's so that you will continue to get an I/O error when you try to read the file that contains that > sector. That doesnt happen. If you get a good read, you wont get an I/O error. > It would be a Very Bad Thing (tm) if you got whatever junk was in the reallocated sector The normal read check stops that from happening, it doesnt have to be flagged as a pending sector to get that. > (remember, the drive could not recover the original data) with no error indication. You will always get an error indication if it couldnt be read, and dont need one if it could be read because the read success varys. > Even if the bad sector is part of your file system's free space or is otherwise irrelevant, the drive has no way to > know that. Yes, but it doesnt need to know that because if its part of the free space it will normally only be written to, not read from. > The drive has to keep the bad sector visible to the OS until you direct a write there, No it does not. It could reallocate the sector on enough bad reads of that sector, and not bother about the data in that sector. > at which point the original content is no longer relevant.
From: Arno on 8 Mar 2010 18:52 In comp.sys.ibm.pc.hardware.storage Ant <ant(a)zimage.comant> wrote: > On 3/7/2010 9:20 AM PT, Arno typed: >> You don't need to, no disk access is possible after a kernel >> panic, hence no loging. The only thing you can do, is to >> look at the screen or to enable the serial console output and >> log that on another machine. >> >> The reason no disk access is possible is simple: A kernel >> panic only hapens when the kernel internal state is regarded >> as seriously corrupted. A disk access could then cause serious >> filesystem corruption (at least writing) and is therefore >> not done. > So Windows' blue screens with memory dumps are different? You can get a memory dump under Linux as well by using the magic sys-req ley (if compiled in), but you cannto write to disk after a panic. It is a safety measure. 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: Arno on 8 Mar 2010 18:53 In comp.sys.ibm.pc.hardware.storage Yousuf Khan <bbbl67(a)spammenot.yahoo.com> wrote: > Arno wrote: >> You don't need to, no disk access is possible after a kernel >> panic, hence no loging. The only thing you can do, is to >> look at the screen or to enable the serial console output and >> log that on another machine. >> >> The reason no disk access is possible is simple: A kernel >> panic only hapens when the kernel internal state is regarded >> as seriously corrupted. A disk access could then cause serious >> filesystem corruption (at least writing) and is therefore >> not done. >> >> Arno > However, it doesn't look like his problems are actually disk related. > The disk-related messages just seem to coincidental and minor. > Yousuf Khan Agreed. 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: Robert Nichols on 8 Mar 2010 19:19
On 03/08/2010 11:24 AM, Rod Speed wrote: > Bob wrote >> Rod Speed wrote >>> Yousuf Khan wrote >>>> Pascal Hambourg wrote >>>>> Rod Speed wrote >>>>>> Pascal Hambourg wrote > >>>>>>> Aren't pending sectors sectors waiting to be remapped because of read errors ? > >>>>>> Thats not the same thing as unreadable sectors. > >>>>> Aren't pending sectors unreadable, because of read errors ? > >>>> Pending sectors are still readable, > >>> Some of them are unreadable, just not all of them are. > >>>> but they are weak when it comes time to write to them. So they are pending remapping during the next write to them. > >>> Even unreadable sectors are marked as pending until the write, so you >>> can attempt to get what data is in them before the write/reallocate. > >> More importantly, it's so that you will continue to get an I/O error when you try to read the file that contains that >> sector. > > That doesnt happen. If you get a good read, you wont get an I/O error. > >> It would be a Very Bad Thing (tm) if you got whatever junk was in the reallocated sector > > The normal read check stops that from happening, it > doesnt have to be flagged as a pending sector to get that. > >> (remember, the drive could not recover the original data) with no error indication. > > You will always get an error indication if it couldnt be read, and > dont need one if it could be read because the read success varys. > >> Even if the bad sector is part of your file system's free space or is otherwise irrelevant, the drive has no way to >> know that. > > Yes, but it doesnt need to know that because if its part of the > free space it will normally only be written to, not read from. > >> The drive has to keep the bad sector visible to the OS until you direct a write there, > > No it does not. It could reallocate the sector on enough bad > reads of that sector, and not bother about the data in that sector. > >> at which point the original content is no longer relevant. You misunderstand. If the bad sectors were actually reallocated, not just marked as "pending", prior to being rewritten, then there would be _no_ error upon reading (the new sector is, after all, good), but the original data from the bad sector could not be there. -- Bob Nichols AT comcast.net I am "RNichols42" |