snapshot implementation

[Ben Schumacher]

On Sun, Dec 27, 2009 at 6:25 PM, Jeff Roberson <jroberson at jroberson.net> wrote:
> It can take some time depending on fs activity on the machine.  There are
> ways to continue to optimize it within the existing infrastructure.  It only
> requires someone willing to expend the time.

Any idea how complex of a task this is (and how much fruit it would
bear)? I've been interested in dipping my toes into some FreeBSD
kernel work, but I'm not exactly sure where to start. I honestly don't
have tons of free time to work on it (job commitments and all that),
but am curious if this is something that an experienced C programmer
would have a shot at doing having very little experience with
low-level kernel internals. (I'm used to dealing with POSIX interfaces
and not the code that implements them...)

I've recently picked up a copy of "The Design and Implementation of
the FreeBSD OS", so I'm starting there, but I would love it if anybody
could toss me a hint or two on what some of the low-hanging fruit in
the arena might be. I've been playing with ZFS on a few boxes now, but
I've had (even with FreeBSD 8) enough unusual crashes that I'm
personally not ready to commit to using it on at least one "mission
critical" project I'm working on. That being said I'd love to be able
to do snapshots on the box without it hanging for over an hour due to
the fact that the data drive is >400GB (frankly on the small side for
some of the storage applications I've read about on this mailing
list).

Any hints, tips, pointers would be appreciated.

Cheers,
Ben