[Lustre-devel] some observations about metadata writeback cache

[Oleg Drokin]

Hello!

On Mar 25, 2009, at 1:52 PM, Alex Zhuravlev wrote:
> RR> Simple clients
> RR> - don't participate in global epochs
>>> hmm. if committed (in terms of transno) request can be reverted
>>> during global recovery, then even simple client has to retain
>>> request on replay list till it's stable in terms of epochs?
> OD> Supposedly, server that performed the operation on behalf of the  
> client
> OD> can do this? So the simple client semantic does not change - the  
> moment
> OD> server has some stable record about hte operation, client can  
> throw the
> OD> data away (otherwise simple clients would need to know how to
> OD> participate
> OD> in rollback/replay even when the server the operation was sent  
> to did
> OD> not
> OD> go down).
> hmm. then wouldn't be simpler to do replay before global recovery  
> and then
> do global replay from server's undo logs?

Yes, but aside from that, losing a caching client leads to global  
recovery,
but losing simple client is not, since server tracks its status.

Bye,
     Oleg