NBD prefetch read

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Hi all.

We need a possibility to ask NBD server to prefetch some data, but do 
not send it to the wire, something like readahead command.
We suggest to realize this possibility by adding a negotiated flag to 
READ command. An alternative may be a separate PREFETCH (or READAHEAD) 
command.
The actual case is the following: we need a managed copy-on-read 
process, where third tool dictates the sequence of copying process, but 
it don't set nor source neither destination.

What do you think?

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Best regards,
Vladimir