To find out if user files are or were affected by bad sectors or bad sector repair (sector reallocation) you can use ‘NFI.exe’. Corrupt data may be even worse than no data at all After all, a few corrupt bits may render all data useless while this isn’t immediately clear. This is probably the most worrying problem. You can use it to verify if any system files were affected (corrupted) and repair them. Windows includes a system file checker (SFC.exe) that can be used to verify system files after sector reallocation. Minor file system damage can be fixed using Chkdsk. A utility like DiskPatch can copy the backup boot sector to the boot sector, or it can even rebuild a boot sector from scratch. Typically Chkdsk will mention the file system is RAW and will refuse repairs. I am not sure how Chkdsk handles this however, I have never seen it happen.Ī corrupt boot sector, which technically is a file as far as NTFS is concerned, could be addressed by using the backup boot sector (which is technically NOT a file, nor part of the file system). Theoretically bad sectors in the first $MFT entries can be overcome by using the $MFTMIRR which backs up the first 4 records of the MFT. You can then use Chkdsk to re-evaluate the bad clusters by specifying /B switch, so chkdsk /b. After all, the clusters that were marked bad no longer contain bad sectors. If we’d run a disk repair utility *after* chkdsk, and let it repair (read: reallocate) bad sectors, the $BADCLUS file would need to be updated. The cluster is marked ‘bad’ at the file system level.Īddressing issues that may occur after sector reallocation on the file system level: This not the same as the disk itself reallocating bad sectors! As far as the disk concerns, the bad sectors still exist. Add the cluster(s) to the $BADCLUS table where it basically marks the cluster as bad so it will not be used again.Determine if a file is affected and if so, try to recover the data from the cluster(s).If chkdsk runs into read problems while scanning clusters it will: A cluster is usually several sectors in size. A cluster is the smallest addressable unit in a file system. A sector is the smallest addressable unit on hard disk. Of course Chkdsk scans at the cluster level rather than the sector level. If the file system itself is affected by bad sectors, the first tool that comes to mind to address those is Chkdsk.exe. There are several possible effects if bad sectors were repaired, depending on what was actually in the sectors.: Were they part ofĪs reallocation of sectors that aren’t in use by any file system or files does not result in data loss, we can ignore this.
#FORMAT DISK WINDOWS 10 FILE SYSTEM AND CLUSTER SOFTWARE#
Which file is affected by a bad sector, if any?Īs this hard disk repair software runs in an out of Windows environment (DOS mostly) and does address the physical disk rather than a logical volume, it has no way of telling if, and if so, which files are affected by the repairs. By writing data to the sector you can signal to the disk that the data is given up on. The disk will not yet reallocate the sector because once it has done that, no attempts can be made to get the data from the sector. When ‘hitting’ a bad sector the disk will add the LBA address of the sector to the ‘pending reallocation’ list. Hard disk repair software scans the disk, allowing the disk to discover bad sectors. From this moment on, all reads and writes to LBA address 100 are redirected to the spare sector that was assigned to this address. utility you can observe and how many sectors have been reallocated this way. The disk all handles this internally:Īssume the sector at LBA address 100 can not be read and is reallocated. If a bad sector develops it can be taken out of service and replaced by one from the spare pool. Hard disks have a pool of ‘spare’ sectors. A commonly asked question is, “how do I determine, which file is affected by a bad sector?”.īad sector repair utilities do not actually repair bad sectors and often the original data in the sector is lost. Hard disk ‘repair’ software like Spinrite, DiskPatch or the hard disk manufacturer diagnostic software often identifies bad sectors in the form of an LBA address (logical block addressing).