Reducing fragmentation impact with forward knowledge in backup systems with deduplication
Michał Kaczmarczyk, Cezary Dubnicki · 2015
Deduplication of backups is very effective in saving storage, but may also cause significant restore slowdown. This problem is caused by data fragmentation, where logically continuous but duplicate data is not placed sequentially on the disk. Two types of fragmentation introduce high restore penalty: inter-version fragmentation, caused by duplicates present in multiple versions of the same backup, and internal fragmentation, caused by duplicates present in a single backup stream.