From mboxrd@z Thu Jan 1 00:00:00 1970 From: Asdo Subject: Re: Question about raid robustness when disk fails Date: Wed, 27 Jan 2010 10:22:36 +0100 Message-ID: <4B6005DC.7070701@shiftmail.org> References: <1262972385.8962.159.camel@kije> <87hbqeyua9.fsf@frosties.localdomain> <7d86ddb91001261619kbb77697t2660e5b8cc44535d@mail.gmail.com> <4877c76c1001262022p369eac60s639d87cad743ff94@mail.gmail.com> <87vden2a2a.fsf@frosties.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-reply-to: <87vden2a2a.fsf@frosties.localdomain> Sender: linux-raid-owner@vger.kernel.org To: Goswin von Brederlow Cc: Michael Evans , Ryan Wagoner , Tim Bock , linux-raid@vger.kernel.org List-Id: linux-raid.ids Goswin von Brederlow wrote: > Michael Evans writes: > >> Why doesn't the kernel issue a pessimistic alternate 'read' path (on >> the other drives needed to obtain the data) if the ideal method is >> late. It would be more useful for time-sensitive/worst case buffering >> to be able to customize when to 'give up' dynamically. >> > > That is a verry good question. I look forward to seeing patches for this > from you. :) I think it isn't done because nobody has bothered to write > the code yet but maybe I'm wrong and it would make the code too > complicated. > This is probably more complicated than allowing a timeout to be set at the MD layer or block-device layer, isn't it? Which would be just as good I think. Is it possible to cancel a SATA/SCSI command that is being executed by the drive? (it's probably feasible only with NCQ disabled anyway, but it's easy to disable NCQ) It's a pity we have to rely on TLER, this narrows the choice of drives a lot...