[Lustre-devel] some observations about metadata writeback cache
Oleg.Drokin at Sun.COM
Wed Mar 25 10:59:25 PDT 2009
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
> OD> can do this? So the simple client semantic does not change - the
> 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
but losing simple client is not, since server tracks its status.
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