From mboxrd@z Thu Jan 1 00:00:00 1970 From: malahal@us.ibm.com Subject: Re: dm mirror with failed device Date: Tue, 23 Sep 2008 09:11:26 -0700 Message-ID: <20080923161126.GA13400@us.ibm.com> References: <200809070211.34360.stephen@octopus-technologies.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <200809070211.34360.stephen@octopus-technologies.com> 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 Stephen Beynon [stephen@octopus-technologies.com] wrote: > This is probably a stupid question, in which case I apologise in advance. > > I am looking to set up a number of machines with internal disks mirrored onto > an iscsi server. I aim to provide resiliance against disk failures, and the > iscsi server will be a handy single point to backup. > > I set up the following test mirror. > > # dmsetup status mirror > 0 16777216 mirror 2 254:8 8:16 32768/32768 0 1 core > # dmsetup table mirror > 0 16777216 mirror core 1 512 2 254:8 0 8:16 0 > > As a test I shutdown the iscsi server and continued writes to the mirror > device. As expected syslog recorded i/o errors on the iscsi lun, but writes > to the mirror continued. After waiting a few minutes I expected to see that > parts of the mirror were out of sync, however dmsetup status gave exactly the > same results as above. > > When I restarted the iscsi server blocks started to be written to the iscsi > server again, but the changes that happened during the iscsi server down time > were never replicated. Clearly this left the mirror in an inconsistent state > with the only indication of problems being in syslog. > > Is there any way I can configure dm-mirror to either mark the blocks as out of > sync when a write fails, and re-try the write later ? > > I am currently running Ubuntu gutsy on the client machines, so it does not > have dmeventd, but from reading the docs it it not clear that dmeventd would > help. What kernel version?