Intel Server RAID Q1 2009 boot camp training lab workbook

Intel

Server RAID Boot Camp Training Q1 2009

C: Impact of I/O queue depth on performance

I/O queuing is important for getting maximum performance out of the RAID subsystem. It

allows sending I/Os to several HDDs in parallel. It also allows getting maximum performance

out of individual HDDs by optimizing heads movement.

Queue depth (or # of Outstanding I/Os) is the number of I/Os that can be issued by an

application in parallel before the first I/O is completed.

Majority of multi-threaded applications use I/O queuing. IOmeter also allows I/O queuing. The

# of Outstanding IOs setting in IOmeter corresponds to the queue depth.

A very common mistake when measuring RAID performance with IOmeter is leaving # of

Outstanding IOs =1, which means no queuing is used. In many cases, this results in

substantially lower performance numbers.

1. On the Access Specification tab, make sure that 64KB Sequential Read is selected.

2. On the Disk Targets tab, set # of Outstanding I/Os = 1.

3. Click the Results Display tab, then click the Green Flag button to start the test and wait for 10

seconds for the test to complete.

4. Record the Total MBs per Second result into the MB/s column in the table below.

5. Repeat steps 2 through 4 for # of Outstanding IOs =2 and =4.

6. Compare the results.

Outstanding IOs MB/s

1 __________ MB/s

_________ MB/s

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