From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: On the subject of RAID-6 corruption recovery Date: Fri, 28 Dec 2007 09:34:58 -0800 Message-ID: <477533C2.6090808@zytor.com> References: <4774663C.5090609@zytor.com> <47750A58.1010702@tmr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <47750A58.1010702@tmr.com> Sender: linux-raid-owner@vger.kernel.org To: Bill Davidsen Cc: Linux RAID Mailing List List-Id: linux-raid.ids Bill Davidsen wrote: > H. Peter Anvin wrote: >> I got a private email a while ago from Thiemo Nagel claiming that some >> of the conclusions in my RAID-6 paper was incorrect. This was >> combined with a "proof" which was plain wrong, and could easily be >> disproven using basic enthropy accounting (i.e. how much information >> is around to play with.) >> >> However, it did cause me to clarify the text portion a little bit. In >> particular, *in practice* in may be possible to *probabilistically* >> detect multidisk corruption. Probabilistic detection means that the >> detection is not guaranteed, but it can be taken advantage of >> opportunistically. > > If this means that there can be no false positives for multidisk > corruption but may be false negatives, fine. If it means something else, > please restate one more time. > Pretty much. False negatives are quite serious, since they will imply a course of action which will introduce further corruption. -hpa