[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [Nbd] [PATCH v2] doc: Add NBD_CMD_BLOCK_STATUS extensio

From: Denis V. Lunev
Subject: Re: [Qemu-devel] [Nbd] [PATCH v2] doc: Add NBD_CMD_BLOCK_STATUS extension
Date: Mon, 4 Apr 2016 23:08:30 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1

On 04/04/2016 11:03 PM, Alex Bligh wrote:
On 4 Apr 2016, at 20:54, Denis V. Lunev <address@hidden> wrote:

for now and for QEMU we want this to expose accumulated dirtiness
of the block device, which is collected by the server. Yes, this requires
external coordination. May be this COULD be the part of the protocol,
but QEMU will not use that part of the protocol.

saying about dirtiness, we would soon come to the fact, that
we can have several dirtiness states regarding different
lines of incremental backups. This complexity is hidden
inside QEMU and it would be very difficult to publish and
reuse it.
So qemu-nbdserver has some idea of 'dirtiness', and you want
to publish that, and the consumer is qemu (and only qemu),
because only qemu knows what 'dirtiness' means in the
sense the server provides it?

I've nothing against helping qemu out here (having
contributed to qemu myself), but perhaps it might be better then,
rather than call it 'dirtiness' to make it some named attribute
for private client/server communication.

This again makes me think this should be a different
command from something which is obviously useful and
comprehensible to more than one server/client (i.e.

original design of this command has used 16 number
to specify the NUMBER of the bitmap which was
exported by the server.

We have reserved number 0 for 'used' bitmap, i.e.
bitmap of allocated blocks and number 1 for 'dirty'
bitmap. Though we can skip specification of the
belonging of any number except '0' and put them
to server-client negotiations. Or we could reserve
'1' for dirtiness state as server-client agrees and
allow other applications to register their own bitmaps
as the deserve to.

Why not to do things this original way?


reply via email to

[Prev in Thread] Current Thread [Next in Thread]