Re: [PATCH 1/2] nbd/proto: introduce structured request

[Wouter Verhelst]

Hi Vladimir,

On Thu, Feb 06, 2020 at 05:10:07PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Hmm, don't you think still, that structured writes may be useful at some
> point? Now we always translate structured read reply to real allocated in RAM
> zeroes. But at some point we may instead propagate this concept to the
> generic block layer, and make support for it in qcow2. Or even with support
> only in NBD we may benefit if we are coping data from one NBD to andother: we
> should not unpack zeroes.

No, I'm with Eric on this one.

It is the client who decides what the size of a request will be. If the
request is too large to handle in one go, the client can just decide to
split it up in multiple requests. The server can't do that, and
therefore needs to be able to split up a single request into multiple
chunks.

The logic that is required client side to reassemble the multiple chunks
with structured requests can already be quite complicated, and it would
be good if we could avoid having that happen on the server side, too.

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