When I ran disk defragmentation on a volume containing Volume Shadow Copy Service (VSS) snapshots, some of my old VSS snapshots were lost. Can I restore them?

A. The VSS snapshot (aka Shadow Copy) creation process copies 16KB blocks as it writes the data to the Shadow Copy storage area (this process is independent of the file system's cluster size). You might encounter a problem if the file system's cluster size is less than 16KB, which can confuse the VSS creation process into not being able to tell the difference between disk defragmentation I/O and normal write I/O. As a result, the VSS creation process performs a copy operation that causes the Shadow Copy storage area to grow very quickly. After the VSS creation process reaches the user-defined limit set for the Shadow Copy storage area, the oldest Shadow Copies will be lost. To resolve this problem, reformat the volumes and use a cluster size of 16KB or larger.

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