From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: [LSF/MM ATTEND][LSF/MM TOPIC] Multipath redesign Date: Wed, 13 Jan 2016 10:10:43 +0100 Message-ID: <56961493.5010901@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Sender: linux-scsi-owner@vger.kernel.org To: "lsf-pc@lists.linux-foundation.org" Cc: device-mapper development , "linux-scsi@vger.kernel.org" List-Id: dm-devel.ids Hi all, I'd like to attend LSF/MM and would like to present my ideas for a=20 multipath redesign. The overall idea is to break up the centralized multipath handling=20 in device-mapper (and multipath-tools) and delegate to the=20 appropriate sub-systems. Individually the plan is: a) use the 'wwid' sysfs attribute to detect multipath devices; this removes the need of the current 'path_id' functionality in multipath-tools b) leverage topology information from scsi_dh_alua (which we will have once my ALUA handler update is in) to detect the multipath topology. This removes the need of a 'prio' infrastructure in multipath-tools c) implement block or scsi events whenever a remote port becomes unavailable. This removes the need of the 'path_checker' functionality in multipath-tools. d) leverage these events to handle path-up/path-down events in-kernel e) move the I/O redirection logic out of device-mapper proper and use blk-mq to redirect I/O. This is still a bit of hand-waving, and definitely would need discussion to figure out if and how it can be achieved. This is basically the same topic Mike Snitzer proposed, but coming from a different angle. But in the end we should be able to do strip down the current=20 (rather complex) multipath-tools to just handle topology changes;=20 everything else will be done internally. Cheers, Hannes --=20 Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N=C3=BCrnberg GF: F. Imend=C3=B6rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG N=C3=BCrnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html