Why TiB calculations from vendor drive specs may result in insufficient TiB vSAN capacity licenses.

Products

• VMware vSAN 8.x

Issue/Introduction

The actual capacity of physical SSDs is slightly larger than what is stated in vendor specifications.

For example, a drive labeled as 15.36 TB is actually 15.360950534144 TB.

When converted to TiB, the specified size is 13.9698 TiB, but the actual size is 13.9707 TiB. While this difference is small for a single drive, it can add up in large vSAN deployments with multiple hosts and drives. As a result, TiB-based calculations using vendor specifications may lead to a slight shortfall in vSAN per-TiB add-on licenses

Environment

vSAN 8.0 U3

Resolution

Broadcom best practices suggest to purchase extra TiB licenses for future growth, this will avoid this issue.

However, if no extra TiB licenses are available, Broadcom recommends purchasing an additional 1 TiB license to account for this small discrepancy and ensure smooth operations.