Subject: Re: [vserver] Another barrier question... Can I "mount" on the barrier?
From: Ed W <lists@wildgooses.com>
Date: Thu, 21 Oct 2010 19:59:39 +0100

On 20/10/2010 22:57, Ed W wrote:
> Hi, I think this has been answered before, but I can't find the 
> question in the archive:
>
> - I have my guest directories as /vserver/images/{guest1,guest2,etc}
> - I would like to put my guests on a different filesystem
>
> I see that I am absolutely fine if my guest filesystem contains 
> "images/guest1" and I mount this on /vserver, because the barrier goes 
> on "images" in the mounted filesystem
>
> However, does it work to create "/vserver/images", put the barrier on 
> that, then "mount /dev/vg/myguests /vserver/images" ?  I thought I saw 
> that this doesn't work, but would like to check and confirm?

Help please..?

Actually, I think the questions boil down to:

- Can the barrier be on the mount point itself? ie given a filesystem 
containing vserver clients, can this be mounted under /vservers/ with 
the barrier on the /vservers/ mount point?

- Where does the barrier go if we bind mount things into multiple 
locations?  eg given a filesystem containing 
"/vservers/{guest1,guest2}", which is mounted at /mnt/vs/.  I then bind 
mount "/mnt/vs/vservers" to /vservers. Where does the barrier now go?  
Presumably it must go on at least /mnt/vs/vservers/ ? Is a barrier also 
needed on /vservers/ ?

Basically I get that the barrier has to go on "/vservers/guest/..", but 
how do things change if we have a bunch of mounts from other 
filesystems, which are then bind mounted into final position?

Just in case this seems too abstract, I'm evaluating some kind of 
clustered filesystem for my guests and for various reasons the guests 
are split between various filesystems.  I'm just trying to understand 
how bind mounting it all together changes where the barrier needs to be.

Thanks

Ed W