Patent ID: 8396833

Claim:
A method for maintaining, in a computer system, data consistency of file system using a first consistency snapshot and a second consistency snapshot, the method comprising: detecting a first group of file transactions; modifying a first i-map in the first consistency snapshot, the modifying the first i-map based on a first sub-group of file transactions of the first group; commencing operations for recording the first consistency snapshot to a persistent storage; for a second sub-group of file transactions of the first group that appear after the commencing operations for recording the first consistency snapshot, performing the following, generating the second consistency snapshot including a second i-map, where the second i-map includes content from the first i-map; detecting that the second sub-group of file transactions allocates inodes represented in the first i-map; determining the inodes are free in the second i-map; allocating the inodes in the first and second i-maps; detecting, after the generating the second consistency snapshot, a second group of file transactions; and modifying, while the operations for recording the first consistency snapshot are occurring, the second i-map of the second consistency snapshot based on the second group of file transactions.