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ADR-065: Windows Desktop OS fallback → VDI Linked Clone

Date: 2026-02-23 Status: Accepted

Context

Analysis of a real 1,483-VM LiveOptics export showed that 92 % of VMs (1,366) fell through to the os_fallback confidence bucket, meaning no VM name pattern matched and only the OS field was used. Of those, ~904 VMs had a Windows 10, Windows 11, or Windows 7 guest OS.

The previous rule (priority 905) classified all Windows Desktop OS VMs as Virtual Machines / VMware / Hyper-V / KVM - No Database, File nor Email with a DRR of 5. While defensible, this misrepresents the actual workload: desktop OS VMs in a datacenter are overwhelmingly VDI endpoints (Citrix PVS, VMware Horizon linked clones, Citrix MCS).

Decision

Change the "Windows Desktop (OS fallback)" rule (priority 905) to classify as:

  • Category: VDI
  • Subcategory: Linked Clone / PVS (Citrix) (DRR = 4)

The OS pattern (windows 10|windows 11|windows 7) is unchanged.

Additionally, add a new "VDI Generic" rule (priority 224, name-based) covering explicit VDI infrastructure keywords: VDI, DESKTOP, RDS, UAG, LOGINVSI, LOGINENTERPRISE.

Rationale

  • In enterprise VMware environments, Windows 10/11 VMs running in a datacenter are almost exclusively VDI linked clones or MCS clones. Physical desktops are not inventoried in RVTools or LiveOptics.
  • VDI Linked Clone (DRR=4) is a conservative estimate; Full Clone (DRR=8) and Instant Clone (DRR=6) are higher. Using the lower value maintains the pre-sales defensibility principle (ADR-005).
  • This change improves the classification rate from ~8 % rule_match to ~75 % on the reference file, making the report far more actionable.

Consequences

  • Positive: ~900 Windows Desktop VMs now get a more accurate workload category and DRR in typical enterprise files.
  • Positive: Engineers reviewing VDI-heavy environments see a realistic capacity estimate, not a generic "Virtual Machines" bucket.
  • Negative: Any genuine Windows 10/11 server-role VM (edge case) will be mis-classified as VDI; engineers can correct via the review grid.
  • Pattern: OS-fallback rules should reflect the most probable datacenter usage of that OS, not the broadest possible category.