[ClusterLabs] Antw: principal questions to a two-node cluster

[Ulrich Windl]

>>> "Lentes, Bernd" <bernd.lentes at helmholtz-muenchen.de> schrieb am 24.04.2015
um
13:07 in Nachricht
<15785B7E063D464C86DD482FCAE4EBA501CAC3CA529F at XCH11.scidom.de>:

> Hi,
> 
> I get the impression that the basic setup is not easy, but very important, 
> because when the cluster is running it is difficult to change something.
> 
> This is my idea:  SAN offers one or more volumes to the nodes ==> disks
which 
> appears in the nodes from the SAN are used as physical volumes ==> physical

> volume/s are combined to a volume group ==> logical volumes are created on
top 
> of this vg, one lv for each virtual machine ==> formatted with a file system

> like ext3 (because each virtual machine does not run concurrently on both 
> nodes this should work) ==> each virtual machine in a raw file, one vm for 
> each lv. In this setup I use cLVM.
> I made a draft (sorry, i'm not an illustrator):  
> https://hmgubox.helmholtz-muenchen.de:8001/f/d4e18bc12a/ 
> The green circle means that I'd like to move a vm to another host, maybe 
> live migration.
> 
> What I like to know:
> 
> - could it work ?
> - is live migration possible with it ?
> - what is about adding a third node later ?

>From some performance tests I had made I got the impression that LVM (or
device mapper) introduces a layer of buffering on top of the multipath device
(or SCSI disks). I'm not sure whether live migration is safe this way. The
experts will tell you, I guess...

> 
> 
> Bernd
> 
> --
> Bernd Lentes
> 
> Systemadministration
> Institut für Entwicklungsgenetik
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> HelmholtzZentrum münchen
> bernd.lentes at helmholtz-muenchen.de 
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> 
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> 
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