Comparing RDS and Nutanix Cluster performance with HammerDB


In a recent experiment using Amazon RDS instance and a VM running in an on-prem Nutanix cluster, both using Skylake class processors with similar clock speeds and vCPU count. The SQLServer database on Nutanix delivered almost 2X the transaction rate as the same workload running on Amazon RDS.

It turns out that migrating an existing SQLServer VM to RDS using the same vCPU count as on-prem may yield only half the expected performance for CPU heavy database workloads. The root cause is how Amazon thinks about vCPU compared to on-prem.

Benchmark Results

HammerDB results from RDS and Nutanix
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Single threaded DB performance on Nutanix HCI


A Nutanix cluster can persist a replicated write across two nodes in around 250 uSec which is critical for single-threaded DB write workloads. The performance compares very well with hosted cloud database instances using the same class of processor (db.r5.4xlarge in the figure below). The metrics below are for SQL insert transactions not the underlying IO.

Single threaded commit heavy insert rates. Latency as seen from SQL insert statement.
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SQL Server uses only one NUMA Node with HammerDB

Some versions of HammerDB (e.g. 3.2) may induce imbalanced NUMA utilization with SQL Server.

This can easily be observed with Resource monitor. When NUMA imbalance occurs one of the NUMA nodes will show much larger utilization than the other. E.g.

Imbalanced NUMA usage by SQL Server.

The cause and fix is well documented on this blog. In short HammerDB issues a short lived connection, for every persistent connection. This causes the SQL Server Round-robin allocation to send all the persistent worker threads to a single NUMA Node! To resolve this issue, simply comment out line #212 in the driver script.

Comment out this line to work-around the HammerDB NUMA imbalance problem.

If successful you will immediately see that the NUMA nodes are more balanced. Whether this results in more/better performance will depend on exactly where the bottleneck is.

Balanced NUMA usage by SQL Server