<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii"> <META NAME="Generator" CONTENT="MS Exchange Server version 6.5.7226.0"> <TITLE>[dm-devel] RE: Multipathing with RHEL4 U2 on EMC DMX</TITLE> </HEAD> <BODY>  A quick update; I noticed that the string I was using to create the multipath device was actually for a failover setup, not multibus. I had been using: # echo "0 141419520 multipath 0 0 2 1 round-robin 0 1 1 8:48 1000 round-robin 0 1 1 8:176 1000" | dmsetup create dm2 From what I can see on Christophe's wiki it should have been the following to get a multibus configuration: # echo "0 141419520 multipath 0 0 1 1 round-robin 0 2 1 8:48 1000 8:176 1000" | dmsetup create dm2 The output of 'multipath -l' for this device now appears as; dm2 () [size=67 GB][features="0"][hwhandler="0"] \_ round-robin 0 [enabled] \_ 0:0:0:6 sdd 8:48 [active][ready] \_ 1:0:0:6 sdl 8:176 [active][ready] I'm not sure if this will fix any of my issues (primarily the LUN dropping off), but wanted to send in this update since my original post had mentioned that I had been thinking about using "failover" instead of "multibus". In reality I was using "failover". I'll see how it goes with my multibus setup, but I'm still curious how you get the settings in /etc/multipath to work. I tried changing the values under the "defaults" section for 'scsi_id' as seen below, but it still keeps using the same command as before. Thanks, David David Child Email David.Child@ps.net _____________________________________________ From: Child, David Sent: Friday, February 10, 2006 8:48 AM To: 'dm-devel@redhat.com' Subject: [dm-devel] Multipathing with RHEL4 U2 on EMC DMX Hello, I've just recently connected some HP BL20p G3 blades running RHEL4 U2 up to a DMX2000 (via McData switches). We didn't get PowerPath and intended to use device-mapper multipathing. I was able to get things up for the most part and get devices defined, but have to do that manually. I've run into a few issues/concerns that I was hoping someone had run across; Kernel: 2.6.9-22.Elsmp Multipath tools: multipath-tools-0.4.6.1-1 Device Mapper: device-mapper-1.01.05-01 1. When running 'multipath -v3' I get errors from the getuid_callout string; "error calling out scsi_id -g -ppre-spc3-83 -u -s /block/sdb". It doesn't like the "-ppre-spc3-83" part. After some research it appears that for the DMX (Symmetrix) a more appropriate string would be "/sbin/scsi_id -g -p 0x80 -u -s /block/sdb". I tried adding that into the 'defaults' section of /etc/multipath.conf, but it doesn't appear to pick it up. I've tried restarting multipathd, rebooting, etc. Is there anyway to get it to take this string? I believe that is part of the problem I'm having with the next item (#2). 2. In order to have multipath working for my EMC devices I have to manually create them on system reboot. I simply created a new startup script for this. Basically I just do; 'echo "0 17677440 multipath 0 0 2 1 round-robin 0 1 1 8:112 1000 round-robin 0 1 1 8:240 1000" | dmsetup create dm0' for each device. Is that normal to have to do that or is there a way to do this automatically? I would suspect it has to do with having a hardware_handler. I thought about the dm-emc handler, but that appears to only work for the CX/AX/FC family (i.e. Clariion) of arrays which work nothing like the Symmetrix. Perhaps if I could get the getuid_callout string working that would help. 3. Early this morning there was a problem on one of the multipath devices used for Oracle ASM; SCSI error : <0 0 0 6> return code = 0x20000 end_request: I/O error, dev sdd, sector 64078960 end_request: I/O error, dev sdd, sector 64078961 device-mapper: dm-multipath: Failing path 8:48. SCSI error : <1 0 0 6> return code = 0x20000 end_request: I/O error, dev sdl, sector 34888112 end_request: I/O error, dev sdl, sector 34888113 device-mapper: dm-multipath: Failing path 8:176. 'multipath -l' showed the device as; dm2 () [size=67 GB][features="0"][hwhandler="0"] \_ round-robin 0 [enabled] \_ 0:0:0:6 sdd 8:48 [failed][ready] \_ round-robin 0 [enabled] \_ 1:0:0:6 sdl 8:176 [failed][ready] The LUNs on this server are shared between three servers and the other two remained on-line so I know the LUN or paths to the array didn't go out. Since the other LUNs on this server remained active I know I didn't loose any HBA connectivity either. The DBAs said they were writing a bunch of data to it when it dropped off line. I ran a few 'multipath' and 'dmsetup status' commands to see what was up and it came back online (it had been "failed" from ~3am to 7am). Should I try using "failover" instead of "multibus" for my "path_grouping_policy"? I would like to have it load balance, but failover is more important. Sorry for the long-winded post. Any help would be appreciated. Thanks, David David Child Email David.Child@ps.net. </BODY> </HTML>