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

[Boaz Harrosh <bharrosh@panasas.com>]

On 11/29/2011 02:47 PM, Trond Myklebust wrote:
> On Tue, 2011-11-29 at 14:40 -0800, Boaz Harrosh wrote: 
>> On 11/29/2011 01:57 PM, Trond Myklebust wrote:
>>>> 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.
>>>
>>> Why would we want to add segment support to the pNFS files client???
>>> Segments are a nuisance that multiply the amount of unnecessary chitchat
>>> between the client and the MDS without providing any tangible
>>> benefits...
>>>
>>
>> Your kidding right?
>>
>> One: it is mandated by the Standard, This is not an option. So a perfectly
>>      Standard complaint server is not Supported by Linux because we don't see
>>      the point.
> 
> Bollocks.. Nothing is "mandated by the Standard". If the server doesn't
> give us a full layout, then we fall back to write through MDS. Why dick
> around with crap that SLOWS YOU DOWN.
> 

NO! MAKE YOU FASTER.

The kind of typologies I'm talking about a single layout get ever 1GB is
marginal to the gain I get in deploying 100 of DSs. I have thousands of
DSs I want to spread the load evenly. I'm limited by the size of the layout
(Device info in the case of files) So I'm limited by the number of DSs I can
have in a layout. For large files these few devices become an hot spot all
the while the rest of the cluster is idle.

This is not a theory, we meet these problems ever day.

>> Two: There are already file-layout servers out there (multiple) which are
>>      waiting for the Linux files-layout segment support, because the underline
>>      FS requires Segments and now they do not work with the Linux client. These
>>      are CEPH and GPFS and more.
> 
> Then they will have a _long_ wait....
> 

OK, so now I understand. Because when I was talking to Fred before BAT and during
It was very very peculiar to me why he is not already done with that simple stuff.
Because usually Fred is such a brilliant fast programmer that I admire, and that simple
crap?

But now that explains

> Trond
> 

Heart