On 7/27/06, Nix, Robert P. <[EMAIL PROTECTED]> wrote:
Not only would you have to shut down all the guests to introduce your maintenance 
(although not during the actual "apply"; you could allocate new disks, copy the 
old ones, and apply your maintenance there, then switch everybody over), you'd also have 
to find a way of tracking changes the maintenance made to the writable directory paths, 
such as /etc. These would be the changes that would bite you in the rear.

This type of set-up was done initially, in order to share a common /usr 
filesystem (I'm not sure the others are really large enough to make a big 
difference, space and cache -wise). But maintaining the system, especially the 
parts and pieces outside the shared filesystem, becomes a nightmare, because 
you can't just use the tools supplied by the vendor to do the maintenance; you 
have to do something extra to catch all the extra fallout. I think, for this 
reason, most people have abandoned the shared /usr concept, and are just 
allocating the space and maintaining each system as if it was a stand-alone 
box. I could be wrong, though.

But you are going through the same thought process that everyone else has at 
some point in this process, so you're in good company.


--
 .~.    Robert P. Nix           Mayo Foundation
 /V\    RO-OC-1-13              200 First Street SW
/( )\   507-284-0844            Rochester, MN 55905
^^-^^   -----
       "In theory, theory and practice are the same, but
        in practice, theory and practice are different."


-----Original Message-----
From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On Behalf Of MOEUR TIM C
Sent: Thursday, July 27, 2006 9:45 AM
To: [email protected]
Subject: Shared common Directories

Hello List,

I'm pursuing an architecture for multiple guests under VM and I'd like
to know if anyone else has done the same, or if this is just an accident
waiting to happen.  I invite your thoughts, comments, and witty remarks.

Here's what I'm considering:  I'd like to create multiple VM  Linux
guests that each have read access to a set of common minidisks.  On
those common minidisks will be what I'm calling the shared Linux file
systems, such as stuff in /sbin, /bin, /boot, /lib.   Each VM Linux
guest will also have an exclusive minidisk (WRITE) that will contain the
file systems needed to update and operate (/etc, /proc, /sys, /tmp and
so on).  The assumption is that each Linux guest will use the same level
of OS, patches, and add-on programs.

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If you are not trying to save disk (we use about 1 Gb for all system
files), why not use something simpler such as unison/rsync to keep all
your files synchronized to a master.  That way, if the disk takes a
hit you won't see all your systems go down.

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