[OpenAFS] Undelete support feedback request

Steve Simmons scs@umich.edu
Mon, 11 Dec 2006 16:55:29 -0500

On Dec 7, 2006, at 8:48 PM, Jason Edgecombe wrote:

> I second Rodney's suggestion. Disclaimer: his office is next to  
> mine ;)
> Being able to have snapshots of a volume or multiple backups of a  
> volume from different times.
> I think the simplest approach would be to clone a volume and give a  
> new but predictable name like vol.backup1 or vol.b20061207
> I don't have a specific need for this at the moment, but it's in my  
> "nice to have" category.
> Jason

Dan Hyde and I have been discussing this for months, and have found a  
few interesting things.

First and foremost, the 'vos clone' command will let you do exactly  
that. The clone persists until removed.

The effective maximum number of clones on a namei file system is 3.  
Seven is the theoretical max, but various volume operations require  
making clones. One or two volume ops starts failing if you've created  
4 clones, more at 5 clones, most at 6. At 7 you can't even  
make .backups. This was all determined experimentally, and damned if  
I can find my notes. Sorry.

Making the excess clones available to the end users is an interesting  
can of worms.

And finally, adding additional clones doesn't help with unremove  
unless you're going to try to make a clone every time a file is  
modified. It's a volume-level activity, not a file-level one.

But that said, we're sure thinking about implementing a larger clone  
set. Just not sure how to go about it. Yet.