Re: bidirectional, long commands + OSD

[James Bottomley <James.Bottomley@steeleye.com>]

On Thu, 2004-01-29 at 08:07, Douglas Gilbert wrote:
> James Bottomley wrote in thread:
> > As I see it, OSD seems to require a different interface from the current
> > bio layer, so there would be some type of object layer glue between the
> > fs and the mid-layer, with the block layer relegated simply to queueing
> > specials for the mid-layer, but since no-one's actually come forward
> > with an implementation, that's just a guess.
> 
> Both Jens and Linus jumped on me when I suggested
> similar heresy :-)

Well ... I merely stated what it seems to require.  I didn't recommend
implementing it.

>From what I can tell, the OSD spec seems to be aimed at large clustered
filesystems.  The recommended mapping seems to be <multiple objects> <->
<one file>.  However, since different objects are distinct and currently
require distinct commands to access them, I believe using OSD for a
typical Linux filesystem would be a big loss because most files are
small and we can no-longer elevate the requests.  It would be
interesting to see if this loss could be offset by not having to do
indirect block lookups, but I have my doubts.

James