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Defragmenter programs can delete System Restore Points
I believe it's possible for any defrag program to cause loss of restore points. It has to do with the Volume Shadow Service cluster size
Shadow copies may be lost when you defragment a volumeThe System Shadow Copy provider uses a copy-on-write mechanism that operates at a 16-KB block level. This is independent of the file system's cluster allocation unit size. If the file system's cluster size is smaller than 16 KB, the System Shadow Copy provider cannot easily determine that disk defragmentation I/O is different from typical write I/O, and performs a copy-on-write operation. This might cause the Shadow Copy storage area to grow very quickly. If the storage area reaches its user-defined limit, the oldest shadow copies are deleted first.
How to Defrag Your Hard Drive ProperlyTrick #3: Don't lose your system restore points!
Lost system restore points in Windows are a common complaint with people using disk defragmenters on machines running Vista and later Windows versions. What happens is the defrag operation moves files around causing the Volume Shadow Copy Service (VSS) to create snapshots that overwrite older ones and cause restore points to get deleted. If you have VSS enabled on your hard drive, or if you are not sure if you do, the first thing you should do after installing Auslogics Disk Defrag is go to Program Settings - Algorithms and set the program to defragment in VSS-compatible mode. This prevents excessive growth of the VSS storage area and ensures that your system restore points will remain intact.
Not all defraggers have this option, so be sure to never use the ones that don't if you have VSS enabled.
8 Reasons Why the Best Windows 7 Defrag is Not the Built-in Windows Disk Defragmenter | Raxco Software Blog#1 Restore Points/VSS
This issue is addressed in Microsoft KB 312067. Defrag activity can purge snapshots off a system. If the drive is formatted in 16K clusters (or a multiple) then steps are taken to minimize purging snapshots or shadow copies. On VSS-enabled drives with a cluster size less than 16K, you need to minimize file movement in order to avoid purging snapshots. By default, PerfectDisk addresses this issue by running in VSS Compatibility Mode with a configurable threshold. The Windows 7 defrag tool has no compatibility mode and will purge the snapshots off a VSS-enabled system.
Defragmenting Files (Windows)Minimizing interactions between defragmentation and shadow copies
When possible, move data in blocks aligned relative to each other in 16-kilobyte (KB) increments. This reduces copy-on-write overhead when shadow copies are enabled, because shadow copy space is increased and performance is reduced when the following conditions occur:
The move request block size is less than or equal to 16 KB.
The move delta is not in increments of 16 KB.
The move delta is the number of bytes between the start of the source block and the start of the target block. In other words, a block starting at offset X (on-disk) can be moved to a starting offset Y if the absolute value of X minus Y is an even multiple of 16 KB. So, assuming 4-KB clusters, a move from cluster 3 to cluster 27 will be optimized, but a move from cluster 18 to cluster 24 will not. Note that mod(3,4) = 3 = mod(27,4). Mod 4 is chosen because four clusters at 4 KB each is equivalent to 16 KB. Therefore, a volume formatted to a 16-KB cluster size will result in all move files being optimized.
Puran Defrag and VSS
"You can uncheck all additional operations in Puran Defrag to run it in VSS compatibility mode. However it is recommended that you format your disk with cluster size > 16K. Please read Puran Defrag help VSS Compatibility section for more info."Puran Defrag and VSS | Wilders Security ForumsSimply excluding "System Volume Information" wont help. Here is the text from Puran Defrag help file "VSS Compatibility" section -
· It is highly recommended that you format your drive with cluster size of 16K if you want to defrag it and also do not want to loose Shadow Copies.
· If above is not possible for you then to configure Puran Defrag so that data movement is minimum and shadow copies are not lost or the loss is minimum, uncheck Additional Operations including Fill Gaps, Optimize Drectories, Free Space and PIOZR.
Some programs have settings to prevent or mitigate this issue, a VSS compatibility mode. Most do not.
Windows by default has a 4K cluster size, and it does not seem wise to change that to a 16K size for this inconsistent issue.
You can determine a drives cluster size by opening a command prompt and typing
fsutil fsinfo ntfsinfo C: (Replace the C with the letter of the drive you want to check)
I think 4k is default? Even my SSD reports that size
Also, you can create a text file in notepad with only 1 character and save it. Right click the new text file> Properties
It will show
Size: 1 bytes (1 bytes)
Size on disk: 4.0KB (4,096 bytes) for example
Showing a cluster size of 4k
I think we can assume that most (if not all) users will not have a cluster size of greater then 16k. I think 4k is set as a reason? Therefore, anyone defragging runs the risk of losing restore points. Since it is not that common, I'll assume free space, and space allocated for SR points are the main causes?
Let's use this thread to discuss the issue. A Guy
Last edited by A Guy; 27 May 2014 at 00:31.