Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive

[Anthony Liguori <anthony@codemonkey.ws>]

On 05/11/2010 08:12 AM, Paul Brook wrote:
>>> cache=always (or a more scary name like cache=lie to defend against
>>> idiots)
>>>
>>>     Reads and writes are cached. Guest flushes are ignored.  Useful for
>>>     dumb guests in non-critical environments.
>>>        
>> I really don't believe that we should support a cache=lie.  There are
>> many other obtain the same results.  For instance, mount your guest
>> filesystem with barrier=0.
>>      
> Ideally yes. However in practice I suspect this is still a useful option. Is
> it even possible to disable barriers in all cases (e.g. NTFS under windows)?
>
> In a production environment it's probably not so useful - you're generally
> dealing with long lived, custom configured guests.
>
> In a development environment the rules can be a bit different. For example if
> you're testing an OS installer then you really don't want to be passing magic
> mount options. If the host machine dies then you don't care about the state of
> the guest because you're going to start from scratch anyway.
>    

Then create a mount point on your host and mount the host file system 
under that mount with barrier=0.

The problem with options added for developers is that those options are 
very often accidentally used for production.

Regards,

Anthony Liguori

> Paul
>
>