Yes, Agreed.
Raid of any level will not change the number of writes in terms of DBWR.
But will change how many physical reads and writes needed to implement
parity and data to the disks.
"Walking on water and developing software from a specification are easy if
both are frozen."
Christopher R. Spence
Oracle DBA
Fuelspot
-----Original Message-----
Sent: Wednesday, May 30, 2001 3:02 PM
To: Multiple recipients of list ORACLE-L
No to be overly pedantic, but RAID5 does not change the number of write()
calls made by DBWR. It will change the number of disk operations done by
your hardware controller or your software raid drivers, but that's slightly
different.
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]>
Sent: Wednesday, May 30, 2001 2:02 PM
> Raid 5 can consume as much as 60% overhead for writes.
>
> "Walking on water and developing software from a specification are easy if
> both are frozen."
>
> Christopher R. Spence
> Oracle DBA
> Fuelspot
>
>
>
> -----Original Message-----
> Sent: Wednesday, May 30, 2001 12:51 PM
> To: Multiple recipients of list ORACLE-L
>
>
> 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
>
> -----Original Message-----
> Sent: Wednesday, May 30, 2001 6:51 AM
> To: Multiple recipients of list ORACLE-L
>
>
> FOR YOUR INFORMATION
>
> ESIS and EPFAL are now part of Logica. The Internet email addresses of the
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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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