White Papers

23 Sizing and Best Practices for Online Transaction Processing Applications with Oracle 11g R2 using Dell PS Series | BP1003
5.3.4 Vdbench (2 TB array capacity utilization, 100% random I/O and 20% data
locality)
Applications such as Oracle OLTP databases typically contain both infrequently accessed and highly dynamic
data within a single volume. The advanced tiering feature on PS6110XS arrays categorizes and operates on
data workloads within each volume.
These workloads are automatically categorized and placed as appropriate onto either SSD or conventional
hard-drive tiers based on the performance requirements on a PS6110XS hybrid array. Typically, in database
applications, there are always specific areas on the disks such as REDO logs which are accessed more
frequently than the other database objects. These frequently accessed objects usually need higher
performance than other database objects.
In order to test the I/O scenario with a specific locality and frequency of I/O access, the Vdbench I/O
generation tool was used to simulate I/O. The ORION tool was not appropriate for this study because there is
no option to specify that the I/O workload accesses a specific locality of data on the disk. A Vdbench test was
run with 20% locality of reference to evaluate the tiering benefits.
The test result showed 7,000 IOPS at the beginning and then gradually increasing to 12,000 over the test
time span. As the test was run, specific portions of the disks were accessed more frequently, and as a result,
more hot pages got created and automatically moved to the SSD tier. This resulted in significant performance
improvement.