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Date: Mon, 21 Jul 2008 17:50:10 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] qcow2 - safe on kill?  safe on power fail?
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To: qemu-devel@nongnu.org

David Barrett wrote:
> Anthony Liguori wrote:
>> Andreas Schwab wrote:
>>> Anthony Liguori <anthony@codemonkey.ws> writes:
>>>  
>>>> The only ways that you can cause corruption is if the QCOW2 sector
>>>> allocation code is faulty (and you would be screwed no matter what 
>>>> here)
>>>> or if you issue a SIGTERM/SIGKILL that interrupts the code while it's
>>>> allocating a new sector.
>>>
>>> Blocking SIGTERM until the allocation is finished could close that 
>>> hole.
>>
>> Seems like a band-aid to me as SIGKILL is still an issue.  Plus it 
>> would involve modifying all disk formats, not just QCOW2.  I'd rather 
>> see proper journal support added to QCOW2 myself.
>
> Well, SIGKILL is a bit more of an extreme case.  SIGTERM seems like a 
> reasonable way to trigger a graceful shutdown (at least, I know I 
> assumed it did for a long time, whereas I'd never assume SIGKILL was 
> graceful).

It would probably be reasonable to trap SIGTERM and to have it trigger 
the equivalent of the "quit" command in the monitor.  Right now, SIGTERM 
will not result in a graceful shutdown of QEMU.

Regards,

Anthony Liguori

> -david
>
>
>