Patent ID: 7200686
Filing Date: 2007-04-03
Classification: G06F

Abstract:
1. A method for processing an IO request for a data storage arrangement where the data storage arrangement allows nonserialized IO requests, the method including the steps of: (a) performing a snapshot protection process for an incoming IO request, the snapshot protection process including (i) determining if the incoming IO request interferes with a file system snapshot mode, and (ii) in the event the incoming IO request interferes with the file system snapshot mode, replacing the incoming IO request with a read request requiring serialization and a write request requiring serialization chained to the read request; (b) after performing the snapshot protection process for the incoming IO request, determining if a first IO request requires serialization, the first IO request comprising either the incoming IO request in the event the incoming IO request does not interfere with the file system snapshot mode, or the read request requiring serialization in the event the incoming IO request interferes with the file system snapshot mode; (c) determining if the first IO request produces an impermissible overlap condition; (d) blocking execution of the first IO request if the first IO request produces the impermissible overlap condition; and (e) initiating execution of the first IO request if the first IO request avoids the impermissible overlap condition.