From mboxrd@z Thu Jan 1 00:00:00 1970 From: malahal@us.ibm.com Subject: Re: Use device mapper to redirect to cache server? Date: Tue, 8 Jan 2008 11:30:42 -0800 Message-ID: <20080108193042.GA6223@us.ibm.com> References: <200801081030.20172.philipp.marek@bmlv.gv.at> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <200801081030.20172.philipp.marek@bmlv.gv.at> 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 Cc: philipp.marek@bmlv.gv.at List-Id: dm-devel.ids Ph. Marek [philipp.marek@bmlv.gv.at] wrote: > Hello everybody! > > > I'd like to mirror write accesses to a block-device to two devices, get all > all *read* accesses from one of these, and if it fails, to fallback to the > other device. This is exactly what 'mirror' target does (dm-raid1.c) without read-balancing. But read on... > The usage would be to use some kind of NAS box as persistent network block > device, with some other machine with a lot of RAM as cache server; the cache > server would get asked for data, and if it's not available, the request > should go to the NAS directly. I think, you are better of using the cache server as some kind of NFS server as 'mirror' target's failure handling is heavy-weight.