Bad Clusters vs. Bad Sectors
in [Storage]
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From: Yousuf Khan on 6 Oct 2009 20:21 Ant wrote: > Hello! > > Am I understanding correctly that these terms are basically the same? If > so, then why did my client's updated Windows 2000 SP4's chkdsk (/r /f > parameters and rebooted to run it) on a HDD (NTFS) in an old Dell > Optiplex system say there was a bad cluster and was able to move a file > to a better place, but I rerun chkdsk in Windows 2000 and ran a chkdsk > (no parameters) and it found 0 KB of bad sector? > > Thank you in advance. :) A sector is an organization system at the hardware level (at one time these used to be called the BIOS level rather than the hardware level), whereas a cluster was an organization unit used by the OS level. Usually a cluster was a multiple of the sector size. If a sector is 512-bytes then the cluster would've been 4 or 8 times that size, or any number really. When you get a bad sector, it's usually the drive itself that is noticing the fault and fixing it itself. This is done quietly in the background, the drive itself reallocates a bad sector to a spare good sector, by copying all of the data over to the spare. Usually you won't see any OS level bad cluster reallocation unless the drive itself has run out of spare sectors. That's when the OS gets involved. If you're run out of spare sectors, then the drive is probably near death already. Yousuf Khan
From: Rod Speed on 6 Oct 2009 23:48 Yousuf Khan wrote: > Ant wrote: >> Hello! >> >> Am I understanding correctly that these terms are basically the >> same? If so, then why did my client's updated Windows 2000 SP4's >> chkdsk (/r /f parameters and rebooted to run it) on a HDD (NTFS) in >> an old Dell Optiplex system say there was a bad cluster and was able >> to move a file to a better place, but I rerun chkdsk in Windows 2000 >> and ran a chkdsk (no parameters) and it found 0 KB of bad sector? >> >> Thank you in advance. :) > > A sector is an organization system at the hardware level (at one time > these used to be called the BIOS level rather than the hardware > level), whereas a cluster was an organization unit used by the OS > level. Usually a cluster was a multiple of the sector size. If a > sector is 512-bytes then the cluster would've been 4 or 8 times that > size, or any number really. > When you get a bad sector, it's usually the drive itself that is > noticing the fault and fixing it itself. This is done quietly in the > background, the drive itself reallocates a bad sector to a spare good sector, by copying all of the data over to the > spare. The drive never does that. The most it ever does is mark it as pending and then reallocates the bad sector on the next write to that sector. > Usually you won't see any OS level bad cluster reallocation unless the drive itself has run out of spare sectors. Thats wrong too. You also see that when the bad sector is not written to again and the OS sees that its bad. > That's when the OS gets involved. Fraid not. > If you're run out of spare sectors, then the drive is probably near death already. Yes, but you cant assume that its run out of bad sectors just because the OS has marked a cluster as bad.
From: Ant on 11 Oct 2009 16:43 On 10/5/2009 12:02 AM PT, Ant typed: >> So sectors is on the hardware and the low-level drivesr, >> while clusters is in the (abstract) filesystem layer. > > Thanks! That makes more sense to me now. I did notice the updated > Windows 2000 SP4's chkdsk /r /f said it found a bad cluster (think it > was TIF file but can't remember and didn't watch the long chkdsk -- > wished it had logging feature or paused to tell me the results before > going back to Windows) and fixed it (moved it). Then, I did a normal > chkdsk.exe in Windows 2000 session's cmd.exe but it didn't show any bad > sectors (0 KB). I was confused there. Is bad block same as bad cluster (OS side)? -- "Thanks for giving me the courage to eat all those ants." --unknown /\___/\ / /\ /\ \ Phil/Ant @ http://antfarm.ma.cx (Personal Web Site) | |o o| | Ant's Quality Foraged Links (AQFL): http://aqfl.net \ _ / Nuke ANT from e-mail address: philpi(a)earthlink.netANT ( ) or ANTant(a)zimage.com Ant is currently not listening to any songs on his home computer.
From: Rod Speed on 11 Oct 2009 20:51 Ant wrote > Ant wrote >>> So sectors is on the hardware and the low-level drivesr, >>> while clusters is in the (abstract) filesystem layer. >> Thanks! That makes more sense to me now. I did notice the updated >> Windows 2000 SP4's chkdsk /r /f said it found a bad cluster (think it >> was TIF file but can't remember and didn't watch the long chkdsk -- >> wished it had logging feature or paused to tell me the results before >> going back to Windows) and fixed it (moved it). Then, I did a normal >> chkdsk.exe in Windows 2000 session's cmd.exe but it didn't show any >> bad sectors (0 KB). I was confused there. > Is bad block same as bad cluster (OS side)? Yes. Is mostly MS OSs that call them clusters.
From: Ant on 12 Oct 2009 04:31
On 10/11/2009 5:51 PM PT, Rod Speed typed: >>>> So sectors is on the hardware and the low-level drivesr, >>>> while clusters is in the (abstract) filesystem layer. > >>> Thanks! That makes more sense to me now. I did notice the updated >>> Windows 2000 SP4's chkdsk /r /f said it found a bad cluster (think it >>> was TIF file but can't remember and didn't watch the long chkdsk -- >>> wished it had logging feature or paused to tell me the results before >>> going back to Windows) and fixed it (moved it). Then, I did a normal >>> chkdsk.exe in Windows 2000 session's cmd.exe but it didn't show any >>> bad sectors (0 KB). I was confused there. > >> Is bad block same as bad cluster (OS side)? > > Yes. Is mostly MS OSs that call them clusters. Ah OK. I guess there was no bad sector then on that old HDD then. -- "When many work together for a goal, great things may be accomplished. It is said a lion cub was killed by a single colony of ants." --Saskya Pandita /\___/\ / /\ /\ \ Phil/Ant @ http://antfarm.ma.cx (Personal Web Site) | |o o| | Ant's Quality Foraged Links (AQFL): http://aqfl.net \ _ / Nuke ANT from e-mail address: philpi(a)earthlink.netANT ( ) or ANTant(a)zimage.com Ant is currently not listening to any songs on his home computer. |