Patent attributes
A storage system that stores verify commands for all the write commands requiring verification in a verify-list that will be processed as a background task is described. The verify-list can include coded data fields that flexibly designate selected alternative states or possibilities for how and where the user data is actually stored. Alternatives for the verify-list include storing the actual raw data, no data, the data in compressed form, a CRC type signature of the data and/or a pointer to a backup copy of the data that is stored either in non-volatile memory such as flash memory or on the disk media in a temporary area. In case of a verification error in various alternative embodiments the user data can be recovered using the backup copy in the verify-list in the write cache, the backup copy in flash memory or on the disk, or from the host.
