Comments on: debian, dell md3000i, dm_multipath and path checking http://blog.loftninjas.org/2008/06/13/debian-dell-md3000i-dm_multipath-and-path-checking/ Tue, 07 Sep 2010 11:37:30 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: Markus Netzlaff http://blog.loftninjas.org/2008/06/13/debian-dell-md3000i-dm_multipath-and-path-checking/comment-page-1/#comment-1946 Markus Netzlaff Tue, 01 Sep 2009 14:50:37 +0000 http://blog.loftninjas.org/?p=201#comment-1946 Hi! I do the same like you: # multipath -ll 36001c23000d59fc600000284478bcdcadm-0 DELL ,MD3000i [size=558G][features=0][hwhandler=1 rdac] \_ round-robin 0 [prio=6][active] \_ 5:0:0:0 sdc 8:32 [active][ready] \_ 8:0:0:0 sdd 8:48 [active][ready] \_ round-robin 0 [prio=0][enabled] \_ 6:0:0:0 sdb 8:16 [active][ghost] \_ 7:0:0:0 sde 8:64 [active][ghost] But after reboot the machine, multipath output nothing. I must move the multipath.conf away, restart the multipath-tools, put the file back and after another daemon restart it works. What is wrong with it? Hi!

I do the same like you:
# multipath -ll
36001c23000d59fc600000284478bcdcadm-0 DELL ,MD3000i
[size=558G][features=0][hwhandler=1 rdac]
\_ round-robin 0 [prio=6][active]
\_ 5:0:0:0 sdc 8:32 [active][ready]
\_ 8:0:0:0 sdd 8:48 [active][ready]
\_ round-robin 0 [prio=0][enabled]
\_ 6:0:0:0 sdb 8:16 [active][ghost]
\_ 7:0:0:0 sde 8:64 [active][ghost]

But after reboot the machine, multipath output nothing. I must move the multipath.conf away, restart the multipath-tools, put the file back and after another daemon restart it works.

What is wrong with it?

]]> By: Vikash http://blog.loftninjas.org/2008/06/13/debian-dell-md3000i-dm_multipath-and-path-checking/comment-page-1/#comment-539 Vikash Mon, 28 Jul 2008 09:52:29 +0000 http://blog.loftninjas.org/?p=201#comment-539 I am trying to configure my MD3000i with multipath on CentOS 5.2. However I am getting quite poor performance when compared to the block device /dev/sdb. The multipath device "/dev/mpath/mpath1" is a round robin on "/dev/sdb" and "/dev/sdc", ie. the 2 ports on the MD3000i. # hdparm -tT /dev/sdb /dev/sdb: Timing cached reads: 4204 MB in 2.00 seconds = 2103.76 MB/sec Timing buffered disk reads: 276 MB in 3.01 seconds = 91.76 MB/sec # hdparm -tT /dev/mpath/mpath1 /dev/mpath/mpath1: Timing cached reads: 4076 MB in 2.00 seconds = 2039.16 MB/sec Timing buffered disk reads: 212 MB in 3.02 seconds = 70.09 MB/sec My server connects via a single Gbe connection to the MD3000i but uses IP alias so that it can connect to both ports on the MD3000i. I can see the lights on the my Gbit switch alternate with a noticeable pause in between whenever I am accessing the LUN via the multipath device. Any idea on how to improve performance? Please let me know if more info is needed. Thanks. I am trying to configure my MD3000i with multipath on CentOS 5.2. However I am getting quite poor performance when compared to the block device /dev/sdb. The multipath device “/dev/mpath/mpath1″ is a round robin on “/dev/sdb” and “/dev/sdc”, ie. the 2 ports on the MD3000i.

# hdparm -tT /dev/sdb

/dev/sdb:
Timing cached reads: 4204 MB in 2.00 seconds = 2103.76 MB/sec
Timing buffered disk reads: 276 MB in 3.01 seconds = 91.76 MB/sec

# hdparm -tT /dev/mpath/mpath1

/dev/mpath/mpath1:
Timing cached reads: 4076 MB in 2.00 seconds = 2039.16 MB/sec
Timing buffered disk reads: 212 MB in 3.02 seconds = 70.09 MB/sec

My server connects via a single Gbe connection to the MD3000i but uses IP alias so that it can connect to both ports on the MD3000i.

I can see the lights on the my Gbit switch alternate with a noticeable pause in between whenever I am accessing the LUN via the multipath device.

Any idea on how to improve performance? Please let me know if more info is needed.

Thanks.

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