Coda File System

Re: Question on coda backups

From: Jan Harkes <>
Date: Fri, 29 Sep 2000 19:01:07 -0400
On Fri, Sep 29, 2000 at 04:50:25PM -0400, Douglas C. MacKenzie wrote:
> backup questions.

A backup volume is a readonly replica that is kept on the server. It
normally doesn't take up that much space because all the files are
shared with the volume it is a backup off (copy-on-write semantics).

So for a doubly replicated volume, let's say vmm:u.hmpierce, we have two
underlying replicas. To distinguish between the two, the createvol_rep
script has created them with numeric suffixes, vmm:u.hmpierce.0 and
vmm:u.hmpierce.1. These underlying volume replicas are the volumes that
actually contain the data on the servers, the replicated volume is
simply a logical volume that only exists in the mind of the Coda client.

So the server that stores the first replica vmm:u.hmpierce.0 will (after
the backup is made) also have a volume vmm:u.hmpierce.0.backup. This is
the readonly clone which is dumped during backups.

A client can mount this volume, because it is still exported by the
servers, but it is unrelated to the volumes on the backup-server (or

Codaservers keep track of previous dumplevels so that they can correctly
select the files required for the incremental (or differential) dump.
The backup program use the dumplevels in /vice/db/dumplevels to pick the
wanted incremental, so that it doesn't always make a full dump.

Does this answer the question, or am I just rambling?
I better go home now.

Received on 2000-09-29 19:30:21