From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: Priozier for remote port on fibre channel devices Date: Fri, 11 Jan 2013 08:22:24 +0100 Message-ID: <50EFBDB0.5010004@suse.de> References: Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: 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 On 01/11/2013 08:11 AM, = Andreas.Bleischwitz@continental-corporation.com wrote: > Hello List, > > I'm currently facing a problem with a storage virtualization device > which is located in two different datacenters and shows up as > another path to a configured SAN-LUN. > The virtualization device is from EMC=B2 and is called V-PLEX. > > So I have something like this: > > DC A > Host ---VPLEX-DC A---LUN storage A > | | > ..|...........|................... > | DC B | > ------VPLEX-DC B---LUN storage B > > The VPLEX device itself is for storage based mirroring and > synchronizes write access to storage A to storage B and the other > way around. > > My problem is, that the virtual LUN I get from the VPLEX does not > have any prioritization given by dm-multipath and looks like this: > > mpath3 (36000144000000010e06d8f12ec30dfef) dm-9 EMC,Invista > [size=3D5.0G][features=3D1 queue_if_no_path][hwhandler=3D0][rw] > \_ round-robin 0 [prio=3D1][active] > \_ 5:0:1:2 sdad 65:208 [active][ready] > \_ 5:0:4:2 sdak 66:64 [active][ready] > \_ 5:0:5:2 sdap 66:144 [active][ready] > \_ 4:0:0:2 sdc 8:32 [active][ready] > \_ 4:0:1:2 sdh 8:112 [active][ready] > \_ 4:0:4:2 sdo 8:224 [active][ready] > \_ 4:0:5:2 sdt 65:48 [active][ready] > \_ 5:0:0:2 sdy 65:128 [active][ready] > > That way, write access is made round-robin and access to the > "remote-devices" - device located in the other DC - creating > duplicate traffic through the > SAN switches as the access has to be routed to the remote VPLEX-B > and it will write to the local VPLEX-A. > > I wanted to solve this problem by giving priorities to a path by its > remote-port - which is different for each connection to a SAN > device. Unfortunately > there currently doesn't exist any priorizer and I have to write one > on my own. > To make the definition flexible, I would like to have a file with a > list of port-wwns associated with a priority. > > For versions shipped with RHEL5 this could be a simple shell script > which simply looks up the sysfs file structures of a given device. > For RHEL6 this has to be > a binary library. So writing a binary version will make more sense > than maintaining two different solutions. > Well, at least on SLES we're shipping a prioritizer named = 'weightedpath' which does exactly this. However, chances are that the VPLEX is supporting ALUA, so you might = want to use the 'alua' prioritizer here. What is the output of 'sg_inq /dev/sdc' ? Cheers, Hannes -- = Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg)