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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>On 03/23/2012 02:41 PM, Hart, Brian R. wrote:<o:p></o:p></p><p class=MsoNormal>(<a href="https://www.redhat.com/archives/dm-devel/2012-March/msg00155.html">https://www.redhat.com/archives/dm-devel/2012-March/msg00155.html</a>)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>> We have a couple of Dell MD storage arrays that when installed<o:p></o:p></p><p class=MsoNormal>> setup multipath.conf to use this line: prio_callout<o:p></o:p></p><p class=MsoNormal>> "/sbin/mpath_prio_rdac /dev/%n"<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>On 03/23/2012 02:41 PM, Bryn M. Reeves wrote:<o:p></o:p></p><p class=MsoNormal>(<a href="https://www.redhat.com/archives/dm-devel/2012-March/msg00155.html">https://www.redhat.com/archives/dm-devel/2012-March/msg00155.html</a>)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>>Callouts make life difficult when file systems go away so like the<o:p></o:p></p><p class=MsoNormal>>path checkers before them they were merged into the libmultipath<o:p></o:p></p><p class=MsoNormal>>shared library. This means that the daemon can lock them into memory<o:p></o:p></p><p class=MsoNormal>>via mlock(2)/mlockall(2) and not have to worry about being able to<o:p></o:p></p><p class=MsoNormal>>load a binary from disk when the paths to that storage have failed -<o:p></o:p></p><p class=MsoNormal>>this is very useful if your root file system is on multipath and you<o:p></o:p></p><p class=MsoNormal>>need to recover from a failure.<o:p></o:p></p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>>In RHEL5 this is dealt with using a complex and fragile private<o:p></o:p></p><p class=MsoNormal>>namespace and RAM-backed file system - the required binaries are<o:p></o:p></p><p class=MsoNormal>>copied into this ramfs at daemon startup and the daemon unmounts<o:p></o:p></p><p class=MsoNormal>>unnecessary file systems to avoid blocking when failures occur.<o:p></o:p></p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>>For this reason the parameter is now just "prio", e.g.:<o:p></o:p></p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>>device {<o:p></o:p></p><p class=MsoNormal>…<o:p></o:p></p><p class=MsoNormal>> prio rdac<o:p></o:p></p><p class=MsoNormal>>}<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I can see that using shared libraries to handle priorities makes handling failed paths easier in many situations. But how to configure active/backup multipath in the following case, for example<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo3'><![if !supportLists]><span style='mso-list:Ignore'>-<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>1st path uses iSCSI over Infiniband<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo3'><![if !supportLists]><span style='mso-list:Ignore'>-<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>2nd path used iSCSI over Gigabit Ethernet<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo3'><![if !supportLists]><span style='mso-list:Ignore'>-<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>iSCSI target does not support ALUA<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo3'><![if !supportLists]><span style='mso-list:Ignore'>-<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>we want Infiniband path to have higher priority<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Will it be enough to set path_grouping_policy = multibus and path_selector = “service-time 0”? Will Gigabit Ethernet path be never used as long as Infiniband path is working?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I appreciate your help,<o:p></o:p></p><p class=MsoNormal> Alexander Murashkin<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Email: AlexanderMurashkin@msn.com<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>