[Lustre-devel] some observations about metadata writeback cache
bzzz at sun.com
Wed Mar 25 09:59:48 PDT 2009
>>>>> Robert Read (RR) writes:
RR> Hi Alex,
RR> I'm trying to figure out how untrusted (what I'm calling simple)
RR> clients and trusted WBC-type clients will work together at the same
RR> time. Simple clients will need to participate in the oldest volatile
RR> epoch calculation, but will need to retain operations for replay.
RR> I've draw a simplified picture of how I think things are beginning to
RR> fit together, but more thought is needed here.
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?
RR> - don't have a node epoch or add epochs to messages
RR> - sends operations to MD server
RR> - replies include extended opaque "replay" data field
probably we could simplify code a lot if we don't need to put
reply into request in order to do replay? IOW, make all request's
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