>On 07/11/2012 12:24 PM, Justin Stringfellow wrote: >>> Suppose you find a weakness in a specific hash algorithm; you use this >>> to create hash collisions and now imagined you store the hash collisions >>> in a zfs dataset with dedup enabled using the same hash algorithm..... >> >> Sorry, but isn't this what dedup=verify solves? I don't see the problem >> here. Maybe all that's n eeded is a comment in the manpage saying hash algorithms aren't perfect. > >It does solve it, but at a cost to normal operation. Every write gets >turned into a read. Assuming a big enough and reasonably busy dataset, >this leads to tremendous write amplification.
If and only if the block is being dedup'ed. (In that case, you're just changing the write of a whole block into one read (of the block) and an update in the dedup date (the whole block isn't written) Casper _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
