copy chunk preliminary results

[David Disseldorp]

On Mon, 04 Nov 2013 10:07:22 +0000
Pádraig Brady <P at draigBrady.com> wrote:

> So cp --reflink has CoW semantics and so probably not an
> appropriate interface for this.  Unless I'm misunderstanding,
> this SMB copy offload does result in a normal copy on the server right?

It depends on how the SMB server interprets the copy-chunk wire request.
On Btrfs, Samba can translate the request into a BTRFS_IOC_CLONE_RANGE
ioctl, in which case the same CoW semantics are observed[1]. See:

https://wiki.samba.org/index.php/Server-Side_Copy#Btrfs_Enhanced_Server-Side_Copy_Offload

By default however, Samba (and Windows) will perform the copy on the
server-side using regular reads/writes. A generic cp --offload or
similar would probably make more sense on the client side.

Cheers, David