[OpenAFS-devel] Re: usage cases for vos create -id and -roid?

[Andrew Deason]

On Sat, 25 Jul 2009 09:37:32 -0400
Jason Edgecombe <jason@rampaginggeek.com> wrote:

> Hi,
> 
> What is a typical usage case for vos create -id and -roid?

vos addsite -roid, too.

First, I want to make clear that these options should almost never be
used, as the manpage (now) states. The actual number of a volume's id
should normally not be of anyone's concern.

The reason the options were created in the first place is because the
inode numbers for files is based on the volume id they reside in. If you
have a large number of files in certain volumes that have
close-to-adjacent volume ids, it's possible to have a case where an
inode number is reused by a different file. In normal operation, you
don't care what inode a particular file is, but some applications depend
on them to be unique (whether or not that's a good idea). -id/-roid
allows you to space such volumes apart if you need to. This obviously
isn't the _only_ way to solve this, but it's one of the easier ways, and
the afs3 protocol allows you to specify ids anyway.

But that's not necessarily the only reason. Conceivably there could be
some AFS-aware software that manipulates volumes based on volume id. Or
maybe something caches volumes by ids, and you needed to remove/recreate
one or something. That's just hypothetical, though; I'm not aware of
anything that actually behaves like that, and doing something like
organizing volumes by id just seems silly.

So, I don't know if I'd consider that a 'typical usage case'. There's
only one actual use case I know of, and it seems atypical.

It would also be trivial to add a -bkid option to 'vos create' at this
point, by the way. I didn't add it because I couldn't think of a use
case.

-- 
Andrew Deason
adeason@sinenomine.net