From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Schinagl Subject: Re: md raid behavior, bad sector uncorrectable read error Date: Sun, 19 Aug 2012 12:39:18 +0200 Message-ID: <5030C256.7080708@schinagl.nl> References: <3E06D7FC-092A-4CB6-B79C-7EC94424DEEE@colorremedies.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Mikael Abrahamsson Cc: Chris Murphy , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 08/19/12 11:47, Mikael Abrahamsson wrote: > On Sat, 18 Aug 2012, Chris Murphy wrote: > >> If the affected chunk is rebuilt from parity (or copy in case of >> mirror), does md raid issue a write command to write the rebuilt chunk >> back to the disk at the same LBAs? If so, shouldn't this force the >> drive to determine if the sector error is transient or persistent, and >> if persistent the disk firmware will remap the bad sector to a reserve >> sector? > > If I remember correctly from what has been described here before, a read > error will cause a re-write with information created from parity, and > the drive should figure it out (either is successfully writes the new > information to the existing sector, or if it can't, it writes it to a > spare sector (re-map)). If it throws a write error, the drive is kicked > from the array (because a drive with write errors is clearly defective). > > So yes, you're correct in your assumption from what I know. > Also, SMARTd would throw up errors when monitoring such drive when a re-map occurs, mdadm may not even notice this if the remap happens successfully.