[Lustre-devel] [RFC] two ideas for Meta Data Write Back Cache

[di wang <di.wang@sun.com>]

> 2) "create w/o name" (this is what MDT accepts these days) isn't operation,
>    it's partial operation. but for partial operations we already have OSD
>    - clear, simple and generic. having one more "partial operations" adds
>    nothing besides confusion, IMHO
>   
I am not sure you can( or should) translate all the MD partial 
operation  into object  RPC for these partial
MD operation.  For example rename,  (a/b  ---> c/d,  a/b in MDS1, c/d in 
MDS2).

     RPC goes to MDS1.

     1) delete d (entry and object) from c in MDS2.
     2) create b entry under c in MDS2.
     3) delete b entry under a in MDS1.

So if you do 1) and 2) by object rpc (skip mdd), then you might need 
create create all 4 objects
(a and b are local object, c and d are remote object),  and permission 
check locally (whether
you can delete d under c). Not sure it is a good way.  And also some 
quota stuff are handled
in these partial operation in remote MDD, so I am not sure we should 
skip mdd totally here.
Am I miss sth?

Thanks
WangDi