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The threshold value of VMware Storage I/O Control defines the upper limit of latency allowed for a datastore. In this best practice, the threshold for storage latency is lowered to optimize performance.
Category | PowerMax Storage |
Product | VMware Storage I/O Control |
Type of best practice | Performance Optimization |
Day and value | Day 3, Fine-tuning |
Overview
Storage I/O Control allows the administrator to manually set a storage latency threshold for the datastores of the virtual machine. The storage latency threshold instructs the Storage I/O Control to monitor datastore(s) to ensure that performance is prioritized if the storage latencies exceed the threshold. In this best practice, the Storage I/O Control threshold is set to 5 milliseconds—the lowest possible value.
Before changing the Storage I/O Control threshold, review VMware’s Set Storage I/On Control Threshold Value for more detail. This VMware guide notes that “a very low value (lower than 20 milliseconds) will result in lower device latency and isolation among I/Os at the potential cost of decrease in aggregate datastore throughput.” As the HammerDB TPC-C workload is characterized by many small reads and writes, throughput was less of a concern. Customers should evaluate if setting the Storage I/O Control threshold would benefit their database workload.
Recommendation
Changing the Storage I/O Control threshold to 5 milliseconds demonstrated a slight performance improvement. Test findings showed minor improvements for:
Database File Sequential Read and Log File Parallel Write saw significant improvement while server CPU utilization slightly increased.
Both TPC-C metrics NOPM and TPM showed a minor improvement; the number of orders completed, and transactions processed slightly increased. Storage IOPS also marginally increased.
Both DB File Sequential Read and Log File Parallel Read Write times showed a slight decrease, indicating faster response times.
Overall, the best practice of changing the Storage Control I/O threshold to 5 milliseconds for the OLTP workload provided minor performance improvements. We recommend implementing this best practice as a post-installation step if further tuning of the database is required to improve storage latencies.
Implementation Steps
Verify that Storage I/O Control is enabled.
References