HIGH QUEUE TIME IS OBSERVED IN THE IORM METRICS (Doc ID 1498191.1)

Last updated on JANUARY 30, 2013

Applies to:

Oracle Exadata Storage Server Software - Version 11.2.2.4.0 to 11.2.3.2.0 [Release 11.2]
Information in this document applies to any platform.

Symptoms

 Performance degradation at the database level. Increase in average IO related waits, without really an increase in the number of waits.

 Aug 28:
 Waits : 734,174        <=====
 Time(s) : 8,107.15
 Avg Time : 11.04      <=====

Sep 14:
Waits : 745,482          <=====
Time(s) : 52,901.47
Avg Time : 70.96        <=====

The above data from AWR report shows that the waits are approximately same i.e 734,174 but the Avg Time increased from 11.04 to 70.96.

 

The IORM is implemented at the storage level.

CellCLI> list iormplan detail
         name:               vxp1cel01_IORMPLAN
         catPlan:
         dbPlan:             name=VCMC,level=1,allocation=30,limit=30
                                 name=VDSH,level=1,allocation=10,limit=10
                                 name=VNAT,level=1,allocation=10,limit=10
                                 name=VMED,level=1,allocation=10,limit=10
                                 name=VCHA,level=1,allocation=25,limit=25
                                 name=VTW,level=1,allocation=10,limit=10
                                 name=other,level=2,allocation=100
         objective:           auto
         status:               active

The above plan shows that limit is set for VCMC database to a max of 30% of the I/O for a given slice of time. VCHA is limited to 25% and the rest get 10% each.

IORM report collected referring Note 1337265.1 shows the high Avg qtime :

 Time: 2012-09-15T04:02:14-06:00

 vxp1cel01: Database: VCMC
 vxp1cel01: Utilization:     Small=0%    Large=6%
 vxp1cel01: Flash Cache:     IOPS=272
 vxp1cel01: Disk Throughput: MBPS=85
 vxp1cel01: Small I/O's:     IOPS=14.2    Avg qtime=70.7ms
 vxp1cel01: Large I/O's:     IOPS=87.1    Avg qtime=288ms    <=========

 Time: 2012-09-15T04:04:14-06:00

 vxp1cel01: Database: VCMC
 vxp1cel01: Utilization:     Small=0%    Large=8%
 vxp1cel01: Flash Cache:     IOPS=499
 vxp1cel01: Disk Throughput: MBPS=113
 vxp1cel01: Small I/O's:     IOPS=45.3    Avg qtime=37.2ms
 vxp1cel01: Large I/O's:     IOPS=113    Avg qtime=413ms    <==========

 

Cause

Sign In with your My Oracle Support account

Don't have a My Oracle Support account? Click to get started

My Oracle Support provides customers with access to over a
Million Knowledge Articles and hundreds of Community platforms