Datafile creation on Mirrored Disks is Twice as Slow as on Non-Mirrored Disks (Doc ID 1382611.1)

Last updated on FEBRUARY 25, 2015

Applies to:

Oracle Server - Enterprise Edition - Version: 11.2.0.2 and later   [Release: 11.2 and later ]
IBM AIX on POWER Systems (64-bit)

Symptoms

The CREATE TABLESPACE command, creating 64Gb datafiles on mirrored and non-mirrored disk shows a big difference in elapsed time, e.g. a duration of 10 minutes for mirrored and 5 minutes for non-mirrored.

Changes

I/O was configured to enable both ASYNC and DIRECT IO (or Concurrent I/O) like in below situation 1.

1) Initial parameters were:
filesystemio_option=setall
disk_asynch_io=true
Mirrored disks = 10 minutes
Non-mirrored disks = 5 minutes

Testing different settings as below:

2)  Forcing Direct I/O
filesystemio_option=directio
disk_asynch_io=true (or false)
Mirrored disks = 10 minutes
Non-mirrored disks = 5 minutes

3)  Forcing Async I/O
filesystemio_option=asynch
disk_asynch_io=true
Mirrored disks = 4.5 minutes
Non-mirrored disks = 4.5 minutes

Cause

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