From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maurice Hilarius Subject: Re: mdadm and TLER (Time Limited Error Recovery) Date: Tue, 08 Sep 2009 19:33:56 -0600 Message-ID: <4AA70604.7020709@harddata.com> References: <299cc2790909071735x6eefd8bsc05ad76fa782cae1@mail.gmail.com> <20090908184837.GA28217@teal.hq.k1024.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090908184837.GA28217@teal.hq.k1024.org> Sender: linux-raid-owner@vger.kernel.org To: Mario 'BitKoenig' Holbe Cc: linux-raid@vger.kernel.org, iusty@k1024.org List-Id: linux-raid.ids Iustin Pop wrote: > .. >> Anyways, clarification... >> The only reason for TLER (Time Limited Error Recovery) is to behave >> "friendly" toward RAID controllers that timeout disks. >> In fact, md does not timeout disks as many Hardware RAID controllers do. >> So, from md's point of view, TLER is useless, i.e. it has no benefit. >> > > I'm sorry but I disagree here. *Especially* because md is used over > normal SATA controllers most of the time, TLER is beneficial because the > drive doesn't go catatonic for minutes at a time trying to recover a bad > sector, which would (because md doesn't timeout disks) cause md to hung > up the whole device. TLER will allow md to see the error quickly and > attempt to rewrite (read) or retry/fail the disk (write) for a bad the > sector. > > Just my understanding of the md stack. > > regards, > iustin > > I agree. Before WD implemented this we would see cases quite often where a perfectly good drive would get "kicked out" of a RAID as frequently or even more often, than on a hardware RAID. TLER management seems to have eliminated most of these cases. -- Regards, Maurice