[linux-lvm] Multiple Path possible with LVM ?

[linux-lvm] Multiple Path possible with LVM ?

["Dr.Peer-Joachim Koch"]

Hi,

is it possible to use to different alternated physical 
pathes with the linux LVM ?
I want to setup a linux server an connect it to a clarrion,
but do not like to pay for the powerpath software from emc.
Under HPUX the lvm handles alternated pathes.
What about linux lvm?
Is there another way to do it ?

    _
   | | - switch1 --  EMC with 2 SP's
   | | - switch2 --/
   |_|

   Linuxbox with 2 HBA's


Thanks and bye Peer

Max-Planck-Institut fuer Biogeochemie
Dr. Peer-Joachim Koch
Carl-Zeiss-Promenade 10      Telefon: ++49 3641 6437-52
D-07745 Jena                 Telefax: ++49 3641 6437-10

Re: [linux-lvm] Multiple Path possible with LVM ?

[Scott Mcdermott]

Dr.Peer-Joachim Koch on Tue  8/07 22:43 +0200:
> is it possible to use to different alternated physical 
> pathes with the linux LVM ?

Just put your lvm volume on an md multipath device.  Note
that these are not loadbalanced paths in stock kernels, just
failover paths.

Re: [linux-lvm] Multiple Path possible with LVM ?

[Lars Grobe]

Hi! 
 
> Just put your lvm volume on an md multipath device.  Note 
> that these are not loadbalanced paths in stock kernels, just 
> failover paths. 
 
Well, in evms 2.1, with 2.4.21 and the md-multipath, I am offered 
a load-balanced multipath configuration. However, as I currently 
have the expensive emc module mentioned in the firt mail ;-), I 
didn't really try this. 
 
If you want to have load balancing, just divide each raidset into 
two luns / "devices", and access each raidset via two paths by this 
configuration. If you put an lvm-stripeset over those two luns, 
you get a "load-balanced" access to your raidset over both channels. 
 
I am currently doing tests with these configurations, but I have moved 
to evms with our new fileserver because of some cluster functionality 
in the 2.x-releases of evms. We have shared storage between two nodes, 
and while you can do this with lvm, it is AFAIK a bit dangerous because 
you must make sure that one nodes commits an vgscan if the other one 
changed the lvm configuration. 
 
Good luck, CU Lars. 

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