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Re: [Qemu-block] [PATCH for-2.6] block: Forbid I/O throttling on nodes w
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-block] [PATCH for-2.6] block: Forbid I/O throttling on nodes with multiple parents for 2.6 |
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Date: |
Wed, 6 Apr 2016 18:01:16 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 |
On 06/04/2016 17:55, Alberto Garcia wrote:
>> > [BB] overlay
>> > |
>> > |
>> > [BDS] qcow2 [BB] backing
>> > | |
>> > +--------------------+
>> > . |
>> > . I/O throttling
>> > . |
>> > [BDS] raw
>> > .
>> > .
>> > .
> I see, thanks for the explanation!
>
> But what's the use of having a BlockBackend on a node that is used as a
> backing image? Is it because "we allow this so let's prevent the user
> from doing weird things", or is there anything useful we can do with it?
The backing image can be the one that is visible to the guest, while the
overlay can be a block-backup target (with 'sync':'none) whose
BlockBackend is created by the NBD server.
Paolo