Setting up replicated filesystems

[Chet Wood]

We recently installed 2 1-gigabyte drives on our Sun 4/370 server called
Luna, to match the same configuration on our other server, called Sol.

Since Sol's disks aren't even anywhere near full, I'm trying to set up a
way to minimize downtime if one of the servers failed. ( Most of our
Sparcstations boot off their own disks.)

I like the way the automounter under 4.1 enables you to mount from
alternative locations. The plan is to have a disk on Sol for "local"
stuff, like X11 and emacs, and a mirror image of it on Luna, mounted
read-only (to force people to make any modifications on the master.)

Then the sparcstations will automount local from whichever server responds
to the mount request.

This makes it easier to do backups, also. A level 0 backup can be done on
the read-only copy without unmounting it.

The slave disk will be updated using rdist in the wee hours. This requires
unmounting it, and mounting it temporarily read-write while rdist does its
thing. It would be nice to be able to update the disk during the day while
people are using it. But I can't think of a way to set up permissions so
that the owner of the rdist process can write to the copy, while nobody
else can. (Without changing permissions in the lower levels of the
heirarchy.)

Another problem is that rdist will not force updates of mode or ownership
changes.  Has anyone else set up a scheme like this, who could comment on
possible solutions?

Thanks in advance...

Chet Wood                       ~                         (408)727-3357
   chet at Advansoft.Com    .  Advansoft Research Corporation
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