> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- > boun...@opensolaris.org] On Behalf Of Sašo Kiselkov > > On 07/11/2012 11:53 AM, Tomas Forsman wrote: > > On 11 July, 2012 - Sa??o Kiselkov sent me these 1,4K bytes: > >> Oh jeez, I can't remember how many times this flame war has been going > >> on on this list. Here's the gist: SHA-256 (or any good hash) produces a > >> near uniform random distribution of output. Thus, the chances of getting > >> a random hash collision are around 2^-256 or around 10^-77. If I asked > >> you to pick two atoms at random *from the entire observable universe*, > >> your chances of hitting on the same atom are higher than the chances of > >> that hash collision. So leave dedup=on with sha256 and move on. > > > > So in ZFS, which normally uses 128kB blocks, you can instead store them > > 100% uniquely into 32 bytes.. A nice 4096x compression rate.. > > decompression is a bit slower though.. > > I really mean no disrespect, but this comment is so dumb I could swear > my IQ dropped by a few tenths of a point just by reading.
Cool it please. You say "I mean no disrespect" and then say something which is clearly disrespectful. Tomas's point is to illustrate that hashing is a many-to-one function. If it were possible to rely on the hash to always be unique, then you could use it as a compression algorithm. He's pointing out that's insane. His comment was not in the slightest bit dumb; if anything, it seems like maybe somebody (or some people) didn't get his point. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
