1. A method comprising: in a network storage server which has a non-volatile mass storage facility, a main cache and a victim cache, generating cache tag information for each of a plurality of data blocks to be stored in the victim cache; storing in the main cache a first subset of the cache tag information for each of the data blocks, and storing in the victim cache a second subset of the cache tag information for each of the data blocks; and reading or writing a data block and corresponding cache tag information for the data block from or to the victim cache, respectively, by appending the corresponding cache tag information to the data block, wherein the data block and corresponding cache tag information read from the victim cache is written to the main cache, and the data block and corresponding cache tag information written to the victim cache is read from the main cache.