New ioctl - FSCTL_DUPLICATE_EXTENTS_TO_FILE
smfrench at gmail.com
Tue Feb 10 00:14:16 MST 2015
On Mon, Feb 9, 2015 at 5:51 PM, David Disseldorp <ddiss at suse.de> wrote:
> On Wed, 28 Jan 2015 19:22:03 +0100, David Disseldorp wrote:
>> > "A new File System Control (FSCTL) has been added to support the new
>> > FSCTL_DUPLICATE_EXTENTS_TO_FILE operation in [MS-FSA]."
>> I haven't played with it yet, but from the [MS-FCC] 20150119 preview
>> doc it looks very similar to copy-chunk, with a few small differences:
>> - It's only supported on ReFS, which may indicate that it's implemented
>> using COW clones.
> The [MS-FSA] draft can be found at:
> It pretty much confirms that it's COW based:
> "The purpose of this operation is to make it look like a copy of a
> region from the source stream to the target stream has occurred when
> in reality no data is actually copied. This operation modifies the
> target stream’s extent list such that, the same clusters are pointed
> to by both the source and target streams’ extent lists for the region
> being copied."
> @Steve, it looks like the perfect candidate for cp --reflink mapping on
> the client side.
agreed. I will take a look against Windows 10 current beta to see if
it accepts or rejects it.
More information about the samba-technical