From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Kus Subject: md-raid paranoia mode? Date: Tue, 10 Jun 2014 23:48:46 -0700 Message-ID: <5397FBCE.3060009@bartk.us> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hello, As far as I understand, md-raid relies on the underlying devices to inform it of IO errors before it'll seek redundant/parity data to fulfill the read request. I have, however, seen certain hard drives report successful reads while returning garbage data. Is it possible to set md-raid into a paranoid mode, in which it reads all available data and confirms integrity? Here's how it would work: RAID6: read data + parity 1 + parity 2. If 1 of the 3 mismatches, correct it, and write corrected data to the corrupt source. Log the event. If all 3 disagree, alert user somehow. RAID5: read data + parity. If they mismatch, alert user somehow. RAID1: read data 1 + data 2. If they mismatch, alert user somehow. You can see this is mostly useful for RAID6 mode, where there is a chance at automated recovery. However, it can also be used to prevent silent data corruption in the other modes, by making it not silent. --Bart