John, have you read Cary Millsap's paper on RAID 5? www.hotsos.com I
believe. RAID 5 will require additional writes by DBWR which is going to be
huge overhead during a dataload.
- Ethan Post
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Peter McLarty wrote
"Are you running RAID and if so what configuration. (Not RAID 5 I hope)"
Interesting. I am posting an excerpt from Doc 97597.1 Optimising Raid
performance for Oracle RDBMS on NT
RAID 5 is useful for Oracle datafiles but not for redo log files or rollback
segments which are sequentially accessed. Datafiles belonging to the
temporary tablespace are not suitable for a RAID 5 device. More benefits
will be seen in situations where reads predominate over writes.
I know that in this instance it is a data load that is being discussed but
presumably once the data is loaded then it will be read more than once.
Certainly the tone of the note suggests that raid 5 is not a definite no-no
rather a 'be cautious as to which files are placed where'. It is my belief
that often a single raid level is set for all files rather than a mix of
raid 1 and raid 5 as appropriate.
Peter, I fully agree that the level of memory utilised here is totally
insufficient and is very likely to be the constraining factor in this case.
John
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