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<P><FONT SIZE=2 FACE="Arial">Hello:</FONT>
<BR> <FONT SIZE=2 FACE="Arial">I have a system with 2 paths to the SAN which is HITACHI HP. The output of multipath -ll is:</FONT>
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<P><FONT SIZE=2 FACE="Arial">mpath2 (360060e8005491000000049100000700a) dm-1 HP,OPEN-V</FONT>
<BR><FONT SIZE=2 FACE="Arial">[size=10G][features=1 queue_if_no_path][hwhandler=0][rw]</FONT>
<BR><FONT SIZE=2 FACE="Arial">\_ round-robin 0 [prio=2][active]</FONT>
<BR><FONT SIZE=2 FACE="Arial"> \_ 3:0:0:1 sdc 8:32 [active][ready]</FONT>
<BR><FONT SIZE=2 FACE="Arial"> \_ 4:0:0:1 sde 8:64 [active][ready]</FONT>
<BR><FONT SIZE=2 FACE="Arial">mpath1 (360060e80054910000000491000007003) dm-0 HP,OPEN-V</FONT>
<BR><FONT SIZE=2 FACE="Arial">[size=10G][features=1 queue_if_no_path][hwhandler=0][rw]</FONT>
<BR><FONT SIZE=2 FACE="Arial">\_ round-robin 0 [prio=2][active]</FONT>
<BR><FONT SIZE=2 FACE="Arial"> \_ 3:0:0:0 sdb 8:16 [active][ready]</FONT>
<BR><FONT SIZE=2 FACE="Arial"> \_ 4:0:0:0 sdd 8:48 [active][ready]</FONT>
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<BR>
<P> <FONT SIZE=2 FACE="Arial">If I run multipathd -k and do show config, there is a lot of out put but I think the key things are: </FONT>
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<P><FONT SIZE=2 FACE="Arial">defaults {</FONT>
<BR><FONT SIZE=2 FACE="Arial"> verbosity 2</FONT>
<BR><FONT SIZE=2 FACE="Arial"> polling_interval 10</FONT>
<BR><FONT SIZE=2 FACE="Arial"> path_grouping_policy multibus</FONT>
<BR><FONT SIZE=2 FACE="Arial"> failback 5</FONT>
<BR><FONT SIZE=2 FACE="Arial"> rr_min_io 10</FONT>
<BR><FONT SIZE=2 FACE="Arial"> no_path_retry 5</FONT>
<BR><FONT SIZE=2 FACE="Arial"> user_friendly_names yes</FONT>
<BR><FONT SIZE=2 FACE="Arial"> bindings_file /etc/multipath.bindings</FONT>
<BR><FONT SIZE=2 FACE="Arial">}</FONT>
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<P><FONT SIZE=2 FACE="Arial">devices {</FONT>
<BR> <FONT SIZE=2 FACE="Arial">LOTS OF DEVICE ENTRIES.</FONT>
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<P><FONT SIZE=2 FACE="Arial"> device {</FONT>
<BR><FONT SIZE=2 FACE="Arial"> vendor (HITACHI|HP)</FONT>
<BR><FONT SIZE=2 FACE="Arial"> product OPEN-.*</FONT>
<BR><FONT SIZE=2 FACE="Arial"> path_checker tur</FONT>
<BR><FONT SIZE=2 FACE="Arial"> failback immediate</FONT>
<BR><FONT SIZE=2 FACE="Arial"> no_path_retry 12</FONT>
<BR><FONT SIZE=2 FACE="Arial"> rr_min_io 1000</FONT>
<BR><FONT SIZE=2 FACE="Arial"> }</FONT>
<BR><FONT SIZE=2 FACE="Arial">}</FONT>
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<P> <FONT SIZE=2 FACE="Arial">The device entry for the SAN has rr_min_io set to 1000. I added rr_min_io 10 in the default, but per the man page for multipath.conf entries in the defaults will only be used if they do not appear other places.</FONT></P>
<P><FONT SIZE=2 FACE="Arial">Q1) If I want to over ride the rr_min_io value in the devices/device section can I just add a devices/device section in /etc./multipath.conf with the things I want to change or do I have to duplicate everything that is in the built-in devices/device entry?</FONT></P>
<P><FONT SIZE=2 FACE="Arial">Q2) How can I determine the best value for rr_min_io?</FONT>
<BR> <FONT SIZE=2 FACE="Arial">I assume whom ever added the HITACHI|HP devices/device built-in entry decide on the value</FONT>
<BR> <FONT SIZE=2 FACE="Arial">of 1000 for a reason. Maybe they did benchmarks or maybe they just copied another entry</FONT>
<BR> <FONT SIZE=2 FACE="Arial">that was some what like what they needed and changed the vendor and product.</FONT>
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<P><FONT SIZE=2 FACE="Arial">I am sure I will have more questions depending on the answers I get to these questions.</FONT>
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<P><FONT SIZE=2 FACE="Arial">-----</FONT>
<BR><FONT SIZE=2 FACE="Arial">Jack Allen</FONT>
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