Re: [Xen-users] How to make network storage high available?

[Ingard Mevåg <ingard.mevag@xxxxxxxxxxxxxx>]

Angel Lopez wrote:
>>>> Unless I really missed something, though, you're going to need ocfs2
>>>>         
>>> or
>>>       
>>>> gfs2 if you're looking to do live migration of xen machines from one
>>>> host to another...
>>>>         
>>> As only one xen host accesses the iscsi-target at a time, it is
>>> sufficient to use a standard journaling file system like ext3, xfs or
>>> reiserfs.
>>>       
>> right, as long as the same volumes are visible from all Dom0's (using CLVM
>> or
>> EVMS-ha), the migrated domU would pick it from the new box.  at this time,
>> the original DomU is already suspended, so it wouldn't be mounted from two
>> kernels at any moment.
>>     
>
> A question about this interesting topic. Is really nedded a cluster aware
> volume manager? I'm asking this because I'm thinking in a scenario where
> two Dom0's access a shared iSCSI disk and the DomU migrates from one Dom0
> to the other one. Do I need a cluster aware filesystem or volume manager
> in that iSCSI shared disk? It would be needed if in the migration process
> the DomU is executed in both Dom0 at the same time, but I'm not sure about
> this.
>
> Thanks.
>   
Hi

I followed this guide: http://www.linux.com/article.pl?sid=06/07/17/1916214

and it worked very well for me for quite a while. However lately I've seen some 
weird errors, such as mounting a LV on one node would report corrupted 
filesystem, or filesystem not found, where it would work fine to mount the LV 
from several other nodes. From what I've gathered, even tho no node is mounting 
the same LV at the same time, problems could arise with using "regular" lvm 
instead of clvm. It is to be said i did export one raided device with AoE and 
then pvcreate etc to create the lvm layer ontop of the aoe share, and maybe, 
just maybe, it is aoe that is making the problem, but seems not. I'd like to 
get some clarification on this matter so if someone would care to elaborate on 
this I would be happy :)

I have heard comments such as "that is insane" about the way aoe and lvm is 
combined in the guide above..


Also, if anyone has any bright ideas on howto easily manage aoe shares
on the "san" side and then mounting each of the /dev/etherd/eX.Y shares
in the domUs instead of creating LVs on top of one share please
elaborate on that as well. I find the numbering scheme AoE uses quite
confusing and difficult to keep track of.

For my personal use, clvm seems to induce a substantial overhead on my
nodes which i really would like to avoid.

Ingard

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