Oracle-L: urgent: lots of db file sequential read

From: chao_ping <chao_ping_at_vip.163.com>
Date: Tue, 25 Feb 2003 12:04:17 -0800
Message-ID: <F001.005590EF.20030225120417@fatcity.com>

hi, friends:
My db server has one poor t3(raid5, 256M Cache) and it is rather slow in disk io. This night, I added a second T3(256M Cache,Raid10) to the database and moved half of datafiles to the second raid. But it seems from statspack, IO wait is more than before:

Statistic                                    Total   per Second    per Trans
--------------------------------- ---------------- ------------ ------------
CPU used by this session                    66,663         23.5          8.2
CPU used when call started                  66,692         23.5          8.2

-------------------------------------------- ------------ ------------ -------
db file sequential read                           225,846      178,026   93.03
log file sync                                       8,604        4,167    2.18
log file parallel write                             8,665        3,593    1.88
db file parallel write                                768        2,455    1.28

now: 66 cpu used /178 cpu waited.
But with the old configuration, cpu used vs cpu waited is like: old: 7832 cpu used / 17508 cpu waited

------------ ------------ ------- db file sequential read 10,164,408 17,508,898 83.50 db file parallel write 46,130 1,072,257 5.11 enqueue 90,498 854,241 4.07

Statistic                                    Total   per Second    per Trans
--------------------------------- ---------------- ------------ ------------
CPU used by this session                 7,832,321        167.4          9.5
CPU used when call started               7,832,333        167.4          9.5

These snapshot are from different time and different time lengh, but I think after i added a disk array to disk array, IO wait should slowdown, but from the new statspack, relatively more time is spent on io wait? How to explain this?
Thanks.

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Author: chao_ping
INET: chao_ping_at_vip.163.com

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