Re: getting creative with cp (was Re: cp -n diff)

[Adam Hamsik <haaaad%gmail.com@localhost>]

On May,Friday 6 2011, at 10:26 PM, David Holland wrote:

> On Fri, May 06, 2011 at 03:45:47PM -0400, der Mouse wrote:
>>> C) Speed it up some more: what if the kernel allowed for "lazy"
>>>   copies to be made when the source & destination were on the same
>>>   filesystem, and the filesystem supported it?
>> 
>> Filesystem-level COW would be a very nice thing to have.  I would
>> question whether it belongs in cp, though, or more precisely whether cp
>> should be aware of it.  I would prefer to have the filesystem
>> autodetect whenever a block is written that is identical in content to
>> a block already present and share the data.  (Yes, what I'm talking
>> about here borders on a content-addressed disk layer.)
> 
> There are filesystems that do that; we just don't have one.
> 
> However, an explicit fast clone operation for directory trees is also
> a nice feature. There are filesystems that do fast clone of whole
> volumes, but I don't think I know of one that does subtrees...

we actually have one in base it's nilfs and reinoud needs to finish it :) and 
there is zfs too.

Regards

Adam.