According to Framingham, Mass.-based IDC, fragmentation occurs when documents are created and then saved or erased.

When a file is first created and saved onto a hard drive or disk, it is stored in contiguous clusters. When the file is later recalled, the head, which reads the information, moves from one cluster to another on a single track. As files are added, they are also set in contiguous clusters. When files are erased, the cluster space they occupied becomes available and is filled as new files are created.

When the new files are larger than the available contiguous space, the information in those files gets broken up and is randomly placed on the disk, and files start to become fragmented. Eventually, the situation deteriorates to the point where performance is severely impacted and files take disproportionate long times to open.

Biller said that problems related to fragmentation are not communicated to consumers, so consumers aren't defragging their flash drives. While Disklace may have a stake in defragmentation because it sells software that can measure the amount of fragmentation in flash drives, Biller is not the only one issuing warnings.

Fragmentation not the issue