On 07/11/2012 09:58 AM, Ferenc-Levente Juhos wrote: > Hello all, > > what about the fletcher2 and fletcher4 algorithms? According to the zfs man > page on oracle, fletcher4 is the current default. > Shouldn't the fletcher algorithms be much faster then any of the SHA > algorithms? > On Wed, Jul 11, 2012 at 9:19 AM, Sašo Kiselkov <skiselkov...@gmail.com>wrote:
Fletcher is a checksum, not a hash. It can and often will produce collisions, so you need to set your dedup to verify (do a bit-by-bit comparison prior to deduplication) which can result in significant write amplification (every write is turned into a read and potentially another write in case verify finds the blocks are different). With hashes, you can leave verify off, since hashes are extremely unlikely (~10^-77) to produce collisions. -- Saso _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
