[Xen-devel] Re: [Xen-users] How to share data between guest domains

[Yura Pismerov <y.pismerov@xxxxxxxxxxxxx>]

I found that using NFS for things like this makes much more sense.
You can run the domU with NFS root (read-only) and map certain areas you
need read/write
to tmpfs by mounting them with "mount --bind" in Linux). For example, if
I use NFS root and want my /etc
be writable I can always write its content to a tmpfs mounted area and
run "mount --bind /tmpfs/etc /etc".
This also will solve problems with centralized package updates when not
only /usr is being updated, but some other areas (eg. /etc, /var/lib).
You want those areas be shared between domU's as well.


Molle Bestefich wrote:

>Todd D. Esposito wrote:
>  
>
>>However, on that note, I wonder if you could mount the same file system,
>>say something like /usr, into multiple domU's READ ONLY.
>>    
>>
>
>That works for me.
>
>What doesn't work is mounting that file/device READ/WRITE in one domU
>to update the filesystem.  For that, I have to take down *all* domUs. 
>Not good...
>
>(When I try I get a vbd: error saying "already in use".)
>
>(I know about caching and that I need eg. a cluster-aware filesystem
>to do this.)
>
>I've spent a couple of hours hunting through various Xen source files.
> There's a lot of Python functions that are only 3-5 lines long and
>which does little else than calling the next function, which makes it
>very hard to figure out what's going on :-/.
>
>Could one of you devel guys please let me know where I need to go to
>remove this silly limitation? :-)
>
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>  
>


-- 
Yuri Pismerov, System Administrator
Armor Technologies (Canada) Inc.

P: 905 305 1946 (x.3519)
http://www.armorware.net

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