Note: This page was only created to give you a brief overview of a specific DiskPatch feature. Before continuing with a procedure please make sure you consult the product manual.

Surface 'defects', are a common cause for data loss; either individual files or folders or entire disks and partitions can become inaccessible due to unreadable sectors. Standard tools included with the Windows operating systems (Chkdsk, Scandisk) only flag unreadable sectors (bad sectors) in the file system, thus making sure the operating system will not to read from or write to the affected clusters. 

Chkdsk and specifically Scandisk can not do anything useful at all when file system specific structures (like the FAT) are affected by bad sectors. DiskPatch addresses sectors a level below the file system. By detecting bad sectors at this level, DiskPatch allows the disk internal error management to reallocate bad sectors; modern hard disks are equipped with a pool of spare sectors which can take the place of a bad sector. The bad sector itself is added to a list of sectors that will never be used again (defect list). In effect, on partitions on which the FAT was cripled by one or more bad sectors and that could not be repaired by Scandisk before, repairs are possible after the bad sectors were reallocated.

Some areas can not be scanned by Chkdsk or Scandisk at all! An example of such a structure is the most important sector on your hard disk (as it is the starting point from which all disk structures on your disk branch); the Master Boot record (MBR).

If DiskPatch detects a bad sector, this is handled using one of the following strategies:

• Error on read that can be corrected: Hard disks apply multiple strategies for correcting 'bad' data allowing the disk to provide you with your data even if a sector could not be read entirely. If the data in a sector can be recovered using this strategy, the data is copied to a spare sector and the bad sector is taken out of service. In addition to the methods the hard disk applies for recovering data, DiskPatch can try more re-reads and disk resets before trying to read again to try to get a 'good read'.
  
  

• Error on read that could not be corrected: If a sector can not be read and the automatic error correction can not recover the data in the sector, the sector will become a candidate for reallocation. A read error will be reported, the data in this sector is lost. The candidate for reallocation will be reallocated when the sector is written to. It is this type of events that will show up in SMART monitoring tools as HD Workbench or SMARTUDM as 'Pending_Reallocation'.
  
  

• Error on write: The bad sector is taken out of service and the data is immediately written to a spare sector. In other words, the bad sector is 'reallocated'. During a read/write surface scan, sectors pending reallocation are reallocated as well. Pending sectors will be removed from the pending 'reallocation list'. The total amount of reallocated sectors and reallocation events can be observed using a SMART utility. Reallocated sectors are also referred to as 'grown defects' list.

Using DiskPatch to scan for and fix bad sectors:

• To run a read-only surface scan:
  
  [Select Disk], [Disk Operations], [Surface Scan (RO)], now select either a partition or select a region manually. To scan the entire disk, select 'entire disk' and leave the suggested default values (just press <enter>).
  
  

• To run a read-write surface scan:
  
  [Select Disk], [Disk Operations], [Surface Scan (RW)], now select either a partition or select a region manually. To scan the entire disk, select 'entire disk' and leave the suggested default values (just press <enter>).

Standard vs. Pro

Please note that the demo and the Standard DiskPatch versions only support read-only surface scanning! 

To run a read/write surface scan you need a DiskPatch Pro or higher version.