Re: NBD prefetch read

[Wouter Verhelst <w@uter.be>]

On Tue, Mar 20, 2018 at 11:57:46AM +0300, Vladimir Sementsov-Ogievskiy wrote:
> 19.03.2018 17:39, Eric Blake wrote:
> > Can you demonstrate an actual sequence of commands sent over the wire,
> > for how it would be useful?
> 
> - we initialize two drives A and B in qemu and setup copy-on-read for them.
> - client send a sequence of READAHEAD commands, and data is copied from A to
> B on read from B, in corresponding sequence.
> 
> So, here B is a cache in terms of the PRE-FETCH command.

This sounds very similar to what xNBD does
(https://bitbucket.org/hirofuchi/xnbd/wiki/Home). Can you confirm?

If so, I suppose it makes sense to add the current behaviour of xNBD to
the spec, rather than inventing our own thing.

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