Thanks! So pool_mp will work with an active-active array like a Symmetrix. I tried pool on powerpath, and it works very well. Thanks, jacob -----Original Message----- From: linux-cluster-bounces@xxxxxxxxxx [mailto:linux-cluster-bounces@xxxxxxxxxx] On Behalf Of Jonathan E Brassow Sent: Tuesday, June 07, 2005 11:57 AM To: linux clustering Subject: Re: GFS Multi-pathing and trespassed LUNs On Jun 6, 2005, at 1:13 AM, <JACOB_LIBERMAN@xxxxxxxx> wrote: > This is a question regarding GFS native multipathing support: > > I have a typical redundant mesh topology -- 2 switches, 2 HBAs per > host, > 2 storage processors. I create the pool device per the procedure > outlined in RedHat KB 4343 and then mount it locally. This works fine. > However, if I trespass the LUN between SPs during a write operation, I > lose all access to it. I have tried pool_mp with both failover and > round robin policies. Unfortunately, pool multipathing does not do any special handling when switching between LUNs - it assumes all LUNs are active/active. This does not seem to be the case in your instance, as trespassing LUNs is a way to do active/passive multipathing (IIRC). So, to answer your questions.... > Here are my questions: > 1. Is there any way to accommodate trespassed LUNs via pool_mp? Short answer: no. Long answer: yes. However, you would have to purchase a copy of PowerPath and use that for multipathing. Pool understands powerpath devices and will sit happily upon them - ignoring the other paths to the device. With multipathing in RHEL4, underlying hardware idiosyncrasies are dealt with properly. > 2. Do you need to do anything special (ie remount the LUN, run > partprobe, etc.) to accommodate a trespassed LUN? If it were possible to make the non-useable LUNs unseen to linux, at least you would have fault tolerance down to the device... However, this would mean that if a controller failed, you wouldn't be able to handle it. > 3. are the pool_mp policies primarily designed to accommodate > front-end failures? (IE cables, HBAs, switch ports.) Again, pool MP requires that all paths are active/active. hope this helps, brassow -- Linux-cluster@xxxxxxxxxx http://www.redhat.com/mailman/listinfo/linux-cluster -- Linux-cluster@xxxxxxxxxx http://www.redhat.com/mailman/listinfo/linux-cluster
