[OpenAFS] Re: Getting started with OpenAFS

Simon Wilkinson sxw@inf.ed.ac.uk
Sun, 2 May 2010 09:15:22 +0100


On 2 May 2010, at 08:35, Dirk Heinrichs wrote:
> But AFAIK the ".<volume>" path is only relevant if RO replicas exist =
for a=20
> given RW volume, right? If there aren't any ROs for an RW, the path is =
also=20
> "/afs/<cellname>/<volume>", isn't it?

Yes. That's right. The other critical thing is that all of the volumes =
from the same cell in the path before a read-only volume must also be =
read-only.=20

When the Unix cache manager encounters a mount point, it determines =
which type of volume to mount by using the following rules:
  *) If there is an explicit type contained in the mount point (ie RW, =
or backup) then it will mount that version of the volume.
  *) If the parent volume (the one which contains the mount point) is =
from a different cell, then it will prefer the read-only version.
  *) Otherwise, it will try to use the type of the parent volume (so if =
the parent is R/O, you'll get a read-only volume, if the parent is a =
backup volume, you'll get a backup volume and so on)

This seems to catch people on IRC out from time to time - they don't =
create a read-only root.cell, and then wonder why no volumes in that =
cell get mounted read only.

Cheers,

Simon.