Re: [kvm-devel] [Qemu-devel] [PATCH] QEMU: fsync AIO writes on flush request

[Paul Brook]

> That'll depend on what kind of device is emulated.  Does the SCSI
> emulation handle multiple in-flight commands with any guarantee on
> order?

SCSI definitely allows (and we emulate) multiple in flight commands.
I can't find any requirement that writes must complete before a subsequent 
SYNCHRONISE_CACHE. However I don't claim to know the spec that well, and it's 
probably not a bad idea have them complete anyway. Preferably this would be a 
completely asynchronous operation. i.e. the sync command returns immediately, 
but only completes when all preceding writes have completed and been flushed 
to disk.

Paul