Re: [PATCH 0/4] nfs41: allow layoutget at pnfs_do_multiple_writes

[Boaz Harrosh <bharrosh@panasas.com>]

On 11/29/2011 01:34 PM, Boaz Harrosh wrote:
> But just do the above and you'll see that it is perfect.
> 
> BTW don't limit the lo_segment size by the max_io_size. This is why you
> have .bg_test to signal when IO is maxed out.
> 
> - The read segments should be as big as possible (i_size long)
> - The Write segments should ideally be as big as the Application
>   wants to write to. (Amount of dirty pages at time of nfs-write-out
>   is a very good first approximation).
> 
> So I guess it is: I hate these patches, to much mess, too little goodness.
> 
> Thank
> Boaz
> 

Ho and one more thing.

Also Files when they will support segments and servers that request segments,
like the CEPH server, will very much enjoy the above, .i.e: Tell me the amount
you know you want to write.

And surly Objects will enjoy that tremendously. Is it a 17 bytes text file, or
the beginning of a big video file.

But the problem with Files and Objects is that they need a layout first before
they can do the right thing in .pg_test and say if this belongs to this IO or
to the next. (Files is stipe_unit maxed+aliened, Objects raid-group boundary)

So your solution is not good for files and Objects, my way solves them two.

Thanks
Boaz