From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tore Anderson Subject: Re: CLARiiON failover modes and DM. Date: Mon, 19 Nov 2007 19:51:28 +0100 Message-ID: <4741DB30.8020009@linpro.no> References: <940B4FF1F5958E4F96FC83C055A2F2611B8C5F@exch-2003.incipient.waltham> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <940B4FF1F5958E4F96FC83C055A2F2611B8C5F@exch-2003.incipient.waltham> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development List-Id: dm-devel.ids * Paul Cote > Is there a specific failover mode that the CX must be set for DM > interoperability? You have (at least) two options. CLARiiON Open mode 1 is the traditional way where all paths to the passive controller is present but will refuse almost all I/O operations. You'll need to be using the "emc" hardware handler for that to work, since a proprietary command needs to be sent to a path to the passive controller in order to trespass the volume there. The other option (which is only available in FLARE 26) is ALUA mode (CLARiiON Open mode 4), where I/O is accepted on both controllers even though only one is the one handling all the I/O. You can use this without a hardware handler (there's one in developement, though), but you'll still want to be prioritising the paths to the preferred controller for optimal performance. This is the mode I would prefer, at least. I wrote a bit more about the ALUA mode a few days ago: http://thread.gmane.org/gmane.linux.kernel.device-mapper.devel/4366/focus=4435 Regards -- Tore Anderson