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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hi,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am sending this as a continuum to the situation described in the following patch:<o:p></o:p></p><p class=MsoNormal><a href="https://patchwork.kernel.org/patch/62094">https://patchwork.kernel.org/patch/62094</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>We are using MD32xxi storage arrays (ISCSI, RDAC) in a clustering environment where we have two machines logged into both controllers of the storage array.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This is the output of multipath –ll on one of the machines when all is well.<o:p></o:p></p><p class=MsoNormal>lun1 (36842b2b00063c13d000003594ce9f82b) dm-1 DELL,MD32xxi<o:p></o:p></p><p class=MsoNormal>[size=1.0T][features=2 pg_init_retries 50][hwhandler=1 rdac][rw]<o:p></o:p></p><p class=MsoNormal>\_ round-robin 0 [prio=200][active]<o:p></o:p></p><p class=MsoNormal>\_ 6:0:0:1 sdf 8:80 [active][ready]<o:p></o:p></p><p class=MsoNormal>\_ 5:0:0:1 sdh 8:112 [active][ready]<o:p></o:p></p><p class=MsoNormal>\_ round-robin 0 [prio=0][enabled]<o:p></o:p></p><p class=MsoNormal>\_ 8:0:0:1 sdj 8:144 [active][ghost]<o:p></o:p></p><p class=MsoNormal>\_ 7:0:0:1 sdk 8:160 [active][ghost]<o:p></o:p></p><p class=MsoNormal>lun0 (36842b2b000571923000003933b4c0d04) dm-0 DELL,MD32xxi<o:p></o:p></p><p class=MsoNormal>[size=1.0T][features=2 pg_init_retries 50][hwhandler=1 rdac][rw]<o:p></o:p></p><p class=MsoNormal>\_ round-robin 0 [prio=200][active]<o:p></o:p></p><p class=MsoNormal>\_ 8:0:0:0 sdd 8:48 [active][ready]<o:p></o:p></p><p class=MsoNormal>\_ 7:0:0:0 sdc 8:32 [active][ready]<o:p></o:p></p><p class=MsoNormal>\_ round-robin 0 [prio=0][enabled]<o:p></o:p></p><p class=MsoNormal>\_ 6:0:0:0 sdb 8:16 [active][ghost]<o:p></o:p></p><p class=MsoNormal>\_ 5:0:0:0 sde 8:64 [active][ghost]<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>When I disconnect the switch connecting between the machines and the storage array (while there is I/O to the devices) and rescan the storage during this period, I get READ_CAPACITY failures and as result the devices receive a zero size. It seems that in this case, not only do we have a ping-pong between path-groups on the same machine, we also have a ping-pong between LUNs on the two machines, which causes havoc to our system.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This was the output of multipath –ll during the failure:<o:p></o:p></p><p class=MsoNormal>lun1 (36842b2b00063c13d000003594ce9f82b) dm-1 ,<o:p></o:p></p><p class=MsoNormal>[size=1.0T][features=2 pg_init_retries 50][hwhandler=1 rdac][rw]<o:p></o:p></p><p class=MsoNormal>\_ round-robin 0 [prio=0][active]<o:p></o:p></p><p class=MsoNormal>\_ #:#:#:# sdf 8:80 [active][undef]<o:p></o:p></p><p class=MsoNormal>\_ #:#:#:# sdh 8:112 [active][undef]<o:p></o:p></p><p class=MsoNormal>\_ round-robin 0 [prio=0][enabled]<o:p></o:p></p><p class=MsoNormal>\_ #:#:#:# sdj 8:144 [active][undef]<o:p></o:p></p><p class=MsoNormal>\_ #:#:#:# sdk 8:160 [active][undef]<o:p></o:p></p><p class=MsoNormal>lun0 (36842b2b000571923000003933b4c0d04) dm-0 ,<o:p></o:p></p><p class=MsoNormal>[size=1.0T][features=2 pg_init_retries 50][hwhandler=1 rdac][rw]<o:p></o:p></p><p class=MsoNormal>\_ round-robin 0 [prio=0][enabled]<o:p></o:p></p><p class=MsoNormal>\_ #:#:#:# sdd 8:48 [failed][undef]<o:p></o:p></p><p class=MsoNormal>\_ #:#:#:# sdc 8:32 [failed][undef]<o:p></o:p></p><p class=MsoNormal>\_ round-robin 0 [prio=0][enabled]<o:p></o:p></p><p class=MsoNormal>\_ #:#:#:# sdb 8:16 [failed][undef]<o:p></o:p></p><p class=MsoNormal>\_ #:#:#:# sde 8:64 [failed][undef]<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Instead of not allowing 0 size paths to enter the map, we should allow them to get in but fail them although the path checker tells us that the path is up.<o:p></o:p></p><p class=MsoNormal>The following patch is over multipathd in device-mapper-multipath-0.4.7-42.el5 (RHEL56):<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>--- a/multipathd/main.c 2010-12-07 08:02:23.000000000 +0200<o:p></o:p></p><p class=MsoNormal>+++ b/multipathd/main.c 2011-02-10 10:51:57.000000000 +0200<o:p></o:p></p><p class=MsoNormal>@@ -1050,4 +1050,11 @@<o:p></o:p></p><p class=MsoNormal> &(pp->checker.timeout));<o:p></o:p></p><p class=MsoNormal> newstate = checker_check(&pp->checker);<o:p></o:p></p><p class=MsoNormal>+ if (newstate != PATH_DOWN) {<o:p></o:p></p><p class=MsoNormal>+ unsigned long long size = 0;<o:p></o:p></p><p class=MsoNormal>+<o:p></o:p></p><p class=MsoNormal>+ sysfs_get_size(sysfs_path, pp->dev, &size);<o:p></o:p></p><p class=MsoNormal>+ if (size == 0)<o:p></o:p></p><p class=MsoNormal>+ newstate = PATH_DOWN;<o:p></o:p></p><p class=MsoNormal>+ }<o:p></o:p></p><p class=MsoNormal> }<o:p></o:p></p><p class=MsoNormal>Since the path is down, the path groups no longer compete on LUN ownership and things remain stable.<o:p></o:p></p><p class=MsoNormal>In addition, with the ping-pong running wild I need to rescan again after storage comes up – with this fix I do not.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Menny<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Trebuchet MS","sans-serif";color:#444444'>Menny Hamburger</span></b><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";color:#444444'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";color:#444444'>Engineer<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";color:#0085C3'>Dell</span></b><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";color:#444444'> | IDC<b><o:p></o:p></b></span></p><p class=MsoNormal><b><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";color:#444444'>office </span></b><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";color:#444444'>+972 97698789<b>, fax </b>+972 97698889<b><o:p></o:p></b></span></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";color:#444444'>Dell IDC. 4 Hacharoshet St, Raanana 43657, Israel</span><span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>