On dim., 2011-05-01 at 23:01 +0200, urgrue wrote: > I've tried all around to find a good solution for my conundrum, without > much luck. > > The point is, multipath works nice. Until a bigger disaster comes along, > e.g. san or datacenter failure. Of course like most big environments you > have a synchronous replica of your SAN. But you have to "do stuff" to > get Linux to take that new LUN and get back to work. A reboot, or san > rescans, forcibly removing disks and so forth. It's not very pretty. > > So my question is, is there any way to get multipath to treat both the > active lun and it's passive replica (usually in readonly or offline > state) as one and the same disk? The goal being, if your SAN fails, you > merely have to activate your DR replica, and multipath would pick it up > and all's well (except for the 30 sec to a few mins of I/O hanging until > the DR was online). In essence, you'd have four paths to a LUN - 2 to > the active one, 2 to the passive one, which is a different LUN > technically speaking (different serials, WWNs, etc), but an identical > synchronous replica (identical data, identical state, identical PVID, etc). > You would have to : 1/ setup a customized getuid program instead of the default scsi_id. (may be based on the pairing id if there is such thing in your context) 2/ set the 'group_by_prio' path grouping policy 3/ develop a prioritizer shared object to assign path priorities based on the master/slave role of the logical unit. Paths to master get prio 2, paths to slave get prio 1. May be someone else can comment on the specific ro->rw promotion issue upon path_group switching. I can't tell if it needs a hw_handler these days. -- Christophe Varoqui OpenSVC - Tools to scale http://www.opensvc.com/ -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
