| 摘要 |
In a method and apparatus for retrieving data from a snapshot data storage system, for each epoch, a snapshot including (i) all changed data, and (ii) an index is created. The index includes an entry for each page that has changed during the epoch. For rapidly retrieving the data as of any given time, the method creates a hash table that includes an entry for each data page that has changed since the baseline was created. The hash table entry indicates the epoch in which the data most recently changed and an offset corresponding to the location of the changed data in the corresponding snapshot. The hash table is created by inserting an entry for each page in the most recent index, and then examining the remaining indices for all other snapshots from the most recent to the oldest snapshot and adding any non-duplicate entries into the table. |
