What is the best practice for configuring VMFS UNMAP for ESXi 6.7 or later?

For VMware ESXi versions 6.7 and later, the recommended best practice is to configure VMFS UNMAP to "Auto with Low Priority." This setting allows the ESXi host to automatically issue UNMAP commands to the FlashArray to reclaim unused space as a background process. The "Low Priority" designation ensures that these space reclamation operations do not interfere with or impact the performance of production I/O from virtual machines. The FlashArray's Purity OS can de-prioritize or throttle the UNMAP commands if the array is busy, maintaining consistent low latency for critical workloads.

A. A fixed rate is a legacy setting that is less flexible than the automatic, load-aware method and is not the current best practice.

B. Setting a high priority could cause UNMAP I/O to compete with production I/O, potentially leading to application performance degradation and latency spikes.

1. Pure Storage, "VMware vSphere with Pure Storage FlashArray Best Practices," Page 29, Section: "VMFS and Automatic UNMAP." The guide states, "Pure Storage recommends leaving this setting at its default of low."

2. Pure Storage Knowledge Base, "VMware ESXi 6.5+ UNMAP/TRIM Best Practices on the FlashArray," Article 000002007. This article details the esxcli command and confirms the recommended priority is low.