The variant of Fletcher that ZFS uses is based on having four sums i. The checksum has a much lower cost compared to a cryptographic hash function such as SHA, but is still significant enough to benefit from optimizations. For this purpose, it makes widespread use of either a Fletcher-based checksum, or a SHA hash. One of its features is protection against data corruption. ZFS is a popular file system originally designed by Sun Microsystems and open sourced. In general the sums are computed modulo M. It computes a number of sums, where C 0 is the sum of the input words, C 1 is the sum of the C 0 sums, etc. Instead of computing the checksum of the input with a traditional linear method, we describe a faster method to split the data into a number of interleaved parallel streams, compute the checksum on these segments in parallel, followed by a recombination step of computing the effective checksum using the partial checksums. Checksums are widely used for checking the integrity of data in applications such as storage and networking.
