RE: ASM is single point of failure ?
- From: "Kevin Closson" <kevinc@xxxxxxxxxxxxx>
- To: "ORACLE-L" <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 9 May 2006 07:49:00 -0700
>>>
>>>Btw, one case when ASM can be in IO codepath is when the ASM
>>>allocation unit -> physical location in datafile isn't
>>>cached in SGA for a particular extent or block range. When
>>>trying to access a block in this range, Oracle server
>>>process makes an OCI call to ASM instance to find out where
>>>a range of blocks is physically located. ASM instance gives
>>>the answer and Oracle DB instance caches this info in SGA
>>>for future use.
...Right a metadata due to the abstraction that would otherwise not
be needed... So if you use ASM on NAS that same sort of metadata
miss can actually happen twice. Once in the Server->ASM level and
then again in the NAS FS->Volmgr level ... I should hope
such misses don't happen much. I don't see any evidence of that
since there would be tare I/Os in the apples workloads comparisons
which I don't see... I see other, um, interesting things, but not that
one as of yet...
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