Oracle 11g new Feature -- I/O calibration

Oracle Database 11g introduces an I/O Calibration mechanism, whereby you can run I/O calibration tests either through the Enterprise Manager Performance page or a PL/SQL package.
--Calibration mechanism 调校机制
--可以在EM中使用也可以使用pl/sql包

Oracle's I/O calibration is a variation on the Clarion tool.

In an Oracle database, the I/O workload is of two basic types--small random I/O and large sequential I/O.
--基本上Oracle Database中的I/O(不限于Oracle Database）分两类： 小的随机I/O,和大量的串行化I/O.

OLTP applications usually experience the small random I/O workload, where the speed with which small I/O requests are serviced is paramount.
--paramount--首要的，

Thus, disk spinning and seeking times are of critical importance.

OLAP applications, on the other hand, employ the large sequential I/O in general.

Oracle uses the following two metrics, each measuring the efficacy of one type of I/O workload:
IOPS(I/O per second): the IOPS rate is the number of small random I/Os the system can perform in a second and depends on the spin speed of disks.
--看样子IOPS是测量小规模随机访问模式的测试工具，而且系统的IOPS指标跟disks的转速有很大关系。

MBPS (megabytes per second) this metric measures the data transfer rate between the server and the storage array and depends on the capacity of the I/O channel between the two systems. A larger I/O channel means a higher MBPS rate.
--MBPS是服务器和存储设备之间传输数据的衡量指标，依赖于I/O的通道，通道越大MBPS越好。


Calibrating I/O Using PL/SQL
You can also use the new procedure CALIBRATE_IO from the DBMS_
RESOURCE_MANAGER package to run the I/O Calibration task. Here is an
example:
begin
exec dbms_resource_manager.calibrate_io(-
num_disks => 1, -
max_latency => 10, -
max_iops => :max_iops, -
max_mbps => :max_mbps, -
actual_latency => :actual_latency);
end;
/
In the CALIBRATE_IO procedure, the following are the key parameters:
■ num_disks Approximate number of disks in the storage array.
■ max_latency Maximum tolerable latency (in milliseconds) for an I/O
request.
■ max_ios Maximum number of random DB block-sized read requests that
can be serviced.
■ max_mbps Maximum number of randomly distributed 1MB reads that can
be serviced (in megabytes per second).
■ actual_latency Average latency of DB block-sized I/O requests at
max_iops rate (in milliseconds).

Once you execute the CALIBRATE_IO procedure, you can query the V$IO_
CALIBRATION_STATUS and the DBA_RSRC_IO_CALIBRATE views to check
the results. Here’s a sample query:
SQL> select max_iops, max_mbps, max_pmbps, latency
from dba_rsrc_io_calibrate;
MAX_IOPS MAX_MBPS MAX_PMBPS LATENCY
---------- ------------ ------------ ----------
133 12 6 64
SQL>
Oracle Database 11g collects I/O statistics in three different dimensions to
provide a consistent set of statistics for I/O calls. These dimensions are
■ RDBMS components grouped into 12 functional groups. The V$IOSTAT_
FUNCTION view provides the details.
■ I/O statistics are collected for each consumer group that’s part of the currently
enabled resource plan. The V$IOSTAT_CONSUMER_GROUP view has
the details.
■ Individual file level I/O statistics are collected and stored in the V$IOSTAT_
FILE view for details.