On Tue, Jan 31, 2012 at 11:28:26AM -0800, Gregory Farnum wrote:

On Tue, Jan 31, 2012 at 11:22 AM, Bernd Schubert
[off-list ref] wrote:

quoted

I guess we should talk to developers of other parallel file systems and see
what they think about it. I think cephfs already uses data integrity
provided by btrfs, although I'm not entirely sure and need to check the
code. As I said before, Lustre does network checksums already and *might* be
interested.

Actually, right now Ceph doesn't check btrfs' data integrity
information, but since Ceph doesn't have any data-at-rest integrity
verification it relies on btrfs if you want that. Integrating
integrity verification throughout the system is on our long-term to-do
list.
We too will be said if using a kernel-level integrity system requires
using DIO, although we could probably work out a way to do
"translation" between our own integrity checksums and the
btrfs-generated ones if we have to (thanks to replication).

DIO isn't really required, but doing this without synchronous writes
will get painful in a hurry.  There's nothing wrong with letting the
data sit in the page cache after the IO is done though.

-chris