Re: [Qemu-devel] Re: [RFC][PATCH] make sure disk writes actually hit disk

[Paul Brook]

> > With a proper async API, is there any reason why we would want this to be
> > tunable?  I don't think there's much of a benefit of prematurely claiming
> > a write is complete especially once the SCSI emulation can support
> > multiple simultaneous requests.
>
> You're right.  This O_SYNC bandaid should probably stay in place
> to prevent data corruption, until the AIO framework is ready to
> be used.

It's arguable whether O_SYNC is needed at all. Qemu doesn't claim data is 
written to disk, and provides facilities for the guest OS to flush the cache, 
just like real hardware does.

Have you measured the impact of O_SYNC? I wouldn't be surprised if it was 
significant.

Paul