From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zdenek Kabelac Subject: Re: block mapping Date: Thu, 29 Sep 2011 16:19:11 +0200 Message-ID: <4E847E5F.5090008@redhat.com> References: <4E8475E3.7020907@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: dm-devel@redhat.com List-Id: dm-devel.ids Dne 29.9.2011 16:10, Kasatkin, Dmitry napsal(a): > Hello, > > > On Thu, Sep 29, 2011 at 4:42 PM, Zdenek Kabelac wrote: >> Dne 29.9.2011 15:35, Kasatkin, Dmitry napsal(a): >>> Hello All, >>> >>> I would like to implement such block device, which can store >>> additional information along with the block data. >>> For example. so if file system has 4k block, I would like to store >>> 4k+256b of additional information... >>> >>> Can such block device be implemented with device mapper? >>> >> >> Yes - i.e.the old snapshot target stores the block and it's remapping info >> (thought the size info is much smaller then 256b) >> > > 1. Old snapshot target? Where is it... > kernel/drivers/md/dm-snap-persistent.c > 2. Isn't it stores some data at the beginning of the block device - in > the header.. A bit more complicated that this - but yes, quite straightforward target. Zdenek