Unmapped I/O

[Konstantin Belousov]

On Fri, Dec 21, 2012 at 12:52:35PM +0100, Ivan Voras wrote:
> On 20 December 2012 21:15, Konstantin Belousov <kostikbel at gmail.com> wrote:
> 
> > Nothing is changed for existing GEOM classes, and it does not mean anything
> > for GEOM developers, unless she wants to change the GEOM class to handle
> > unmapped BIOs.
> 
> Understood, but the intention of my question was: do you recommend
> GEOM classes should take the effort and implement unmapped BIOs
> whenever possible?
Depends. RAID 0 and RAID 1 can process unmapped BIOs without changes,
I am sure. For the class like RAID5, you would need a hardware
for it to be able to operate on the unmapped BIOs without requiring
the remap. There is indeed Intel IOAT, which I believe can do this.

On the other hand, for encrypting classes like GELI it probably does not
make much sense to care, for the case of encryption done in software or
using AES-NI.

> 
> Your change in g_part.c is trivial - this is because g_part doesn't
> actually touch the BIO data, only pass it on?
Right.
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