Re: [Qemu-block] [Nbd] [Qemu-devel] How to online resize qemu disk with nbd protocol?

[Bob Chen]

There might be a time window between the NBD server's resize and the client's `re-read size` request. Is it safe?

What about an active `resize` request from the client? Considering some NBD servers might have the capability to do instant resizing, not applying to LVM or host block device, of course...

Regards,

Bob

2017-01-13 0:54 GMT+08:00 Stefan Hajnoczi <address@hidden>:

On Thu, Jan 12, 2017 at 3:44 PM, Alex Bligh <address@hidden> wrote:
>> On 12 Jan 2017, at 14:43, Eric Blake <address@hidden> wrote:
>> That's because the NBD protocol lacks a resize command.  You'd have to
>> first get that proposed as an NBD extension before qemu could support it.
>
> Actually the NBD protocol lacks a 'make a disk with size X' command,
> let alone a resize command. The size of an NBD disk is (currently)
> entirely in the hands of the server. What I think we'd really need
> would be a 'reread size' command, and have the server capable of
> supporting resizing. That would then work for readonly images too.

That would be fine for QEMU.  Resizing LVM volumes or host block
devices works exactly like this.

Stefan