#Tech Tips# Engineering Guide: How to Calculate True Usable Space on Sangfor aSAN (2-Copy vs. 3-Copy Policy)
  

George Fady Lv2Posted 2026-Jun-30 19:00

Sizing a hyper-converged storage pool isn't as simple as adding up the raw capacity of your drives. When architecting Sangfor Hyper-Converged Virtual Storage (aSAN), we have to account for fault-tolerance storage overhead and system file reservations.

If you cross the line, you risk pool exhaustion. Let's look at the actual math for standard enterprise deployments:
1. Usable Capacity under a 2-Copy Policy: When configuring standard two-replica disk fault tolerance, the formula to safely calculate available capacity must include an 85% utilization safety threshold to avoid performance write-locks:

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Humayun Ahmed Lv4Posted 2026-Jul-01 13:21
  
Thanks to share!
Sangfor Jojo Lv5Posted 2026-Jul-08 17:45
  
This is really useful, thanks for breaking it down like that.