[SeaBIOS] [PATCH] fix two issues with virtio-blk

[Gleb Natapov]

On Sun, May 16, 2010 at 03:34:23PM +0200, Sebastian Herbszt wrote:
> Gleb Natapov wrote:
> >On Sat, May 15, 2010 at 10:08:54PM +0200, Sebastian Herbszt wrote:
> >>Why is a 4 KB physical sector size needed in a VM anyway?
> >>
> >Performance of course. Qemu today can advertise physical block size and
> >logical block size greater then 512 with virtio. The problem is that if
> >logical block size != 512 boot fails.
> >
> >--
> >Gleb.
> 
> Which OS currently has native support for 4 KB sectors and how big is the
> performance gain?
I believe at least Linux has it. Windows 7 aligns partition to 4K, so
it either has it too, or ready to gain it any moment.

>                   The performance without native support (emulation in 
> BIOS) could be worse due to the additional overhead. How much performance
> is lost if the 512 byte logical sector size emulation is done in virtio (for reads
> it could behave like a read ahead buffer) ?
Low performance of BIOS emulation is not a concern. BIOS is used only by
boot loaders. OSes access disk without BIOS help.

--
			Gleb.