From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Evans Subject: Re: when read error ,where do we rewrite? Date: Thu, 7 Jan 2010 22:35:29 -0800 Message-ID: <4877c76c1001072235m2790209exe0601e410889d52f@mail.gmail.com> References: <6c394cc31001070441r1287f635q9c58dc836ce488b7@mail.gmail.com> <20100107131855.GA10915@cthulhu.home.robinhill.me.uk> <6c394cc31001072054v7368cc05kb7005b39d00c1c07@mail.gmail.com> <6c394cc31001072059t2669afa8l5fed42ff77b3c134@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <6c394cc31001072059t2669afa8l5fed42ff77b3c134@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: dong wu Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thu, Jan 7, 2010 at 8:59 PM, dong wu wrote: > In the source code of raid5,when write error,it faulty the disk,not r= emap > the block. why do it use "remap the block"? > > 2010/1/8, dong wu : >> If it is written to the same block,will it read error again? >> when read error,the low-level attempts a write and remap the block i= f >> the write fails. >> where does it remap? >> Is there any spare block in the disk for remap when read or write er= ror occurs? >> >> 2010/1/7, Robin Hill : >> > On Thu Jan 07, 2010 at 08:41:20PM +0800, dong wu wrote: >> > >> > > when read error and can rewrite,where do we rewrite? >> > > It can't be rewrited to the old block. >> > > It should be rewrite to other place,where can we find the 'other= place'? >> > > In the source code,I don't find the place that should be rewrite= d to. >> > > >> > It's rewritten to the same block - it's up to the low-level device= (the >> > disk) to attempt a write and transparently remap the block if the = write >> > fails. >> > >> > Cheers, >> > =A0 =A0Robin >> > -- >> > =A0 =A0 ___ >> > =A0 =A0( ' } =A0 =A0 | =A0 =A0 =A0 Robin Hill =A0 =A0 =A0 =A0 | >> > =A0 / / ) =A0 =A0 =A0| Little Jim says .... =A0 =A0 =A0 =A0 =A0 =A0= =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| >> > =A0// !! =A0 =A0 =A0 | =A0 =A0 =A0"He fallen in de water !!" >> > >> > >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid"= in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =A0http://vger.kernel.org/majordomo-info.html > Modern mass storage devices provide an /abstraction/ of a linear storage device which needn't actually be so. On most of them data plus some extra parity for recovery are stored; if the drive has unusual trouble reading the data back, it will try to get a good read/repair and then use another, spare (reserved), area on the device in place of the one that 'went bad'. This is actually a major problem for cryptographic/security concerns, and is one possible metric in S.M.A.R.T. data that can indicate a failing drive. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html