Excerpts from internet.info-afs: 22-May-96 Re: Replication Advice? by
Jeffrey [EMAIL PROTECTED]
> That's about it. The cache manager will only look for readonly volumes
> if you're still on a "read-only" path - that is, if all volumes traversed
> from /afs on down have been read-only volumes. This means that once you
> go through a "read/write" mount point (e.g., a mount point for "%root.afs"
> instead of "#root.afs"), you always get read/write volumes.
>
> If you want to actually be able to _change_ the contents of a replicated
> volume, you'll have to have such a "read/write" mount point.
The last sentence isn't quite true. You don't _need_ to have a
read/write mount point (created with "fs mkmount -rw") in order to
change a replicated volume. Using the /afs/.cell-name read/write mount
point is a handy convention for changing most replicated volumes, but a
read/write mount point isn't required to make changes.
Another trick I typically use for modifying the replicated root.afs
volume is to create a temporary mount point in my home directory. In my
home directory, I create a normal mount point for the volume I want to
change. Since I know my home directory is in a volume that's not
replicated, I know that the cache manager won't use the read-only volume
when traversing any mount points it contains.
As an example, here's a new mount point created in my home directory.
The "fs listquota" command shows that the read/write volume is selected
when "tmp" is traversed since the output doesn't show
"root.afs.readonly".
[~] fs mkm tmp root.afs
[~] fs lq tmp
Volume Name Quota Used % Used Partition
root.afs 1000 306 31% 50%
The exception to this rule, as Jeff pointed out, is for cross-cell mount
points. If the mount point contains a cell name (by using the "fs
mkmount -cell" option), the cache manager will select the read-only
volume, if one exists. Note that it doesn't matter if the given cell
name is a remote cell or the local cell; any cell name in the mount
point enables the read-only selection.
Here's another example where I use the -cell option even though
"psc.edu" is my local cell name. This time I get the ".readonly" volume.
[~] fs mkm tmp2 root.afs -cell psc.edu
[~] fs lq tmp2
Volume Name Quota Used % Used Partition
root.afs.readonly 1000 306 31% 50%
Joe Jackson,
Pittsburgh Supercomputing Center.
