We used Iometer to generate several workloads that simulate various I/O encountered in Virtual SAN production environments. These are shown in the following table.
|Type of I/O workload||Size (1KiB = 1024 bytes)||Mixed Ratio||Shows / Simulates|
|All Read||4KiB||–||Maximum random read IOPS that a storage solution can deliver|
|Mixed Read/Write||4KiB||70% / 30%||Typical commercial applications deployed in a VSAN cluster|
|Sequential Read||256KiB||–||Video streaming from storage|
|Sequential Write||256KiB||–||Copying bulk data to storage|
|Sequential Mixed R/W||256KiB||70% / 30%||Simultaneous read/write copy from/to storage|
In addition to these workloads, we studied Virtual SAN caching tier designs and the effect of Virtual SAN configuration parameters on the Virtual SAN test bed.
Virtual SAN 6.0 can be configured in two ways: Hybrid and All-Flash. Hybrid uses a combination of hard disks (HDDs) to provide storage and a flash tier (SSDs) to provide caching. The All-Flash solution uses all SSDs for storage and caching.
Tests show that the Hybrid Virtual SAN cluster performs extremely well when the working set is fully cached for random access workloads, and also for all sequential access workloads. The All-Flash Virtual SAN cluster, which performs well for random access workloads with large working sets, may be deployed in cases where the working set is too large to fit in a cache. All workloads scale linearly in both types of Virtual SAN clusters—as more hosts and more disk groups per host are added, Virtual SAN sees a corresponding increase in its ability to handle larger workloads. Virtual SAN offers an excellent way to scale up the cluster as performance requirements increase.
You can download Virtual SAN 6.0 Performance: Scalability and Best Practices from the VMware Performance & VMmark Community.