Storage Tiering Service · View 23 of 31 · 6 · Operations
Decisions
- Policies are CUE in Git. Validation rejects any policy that names a price, a latency or a vendor class; those come from the ladder, so a policy cannot quietly disagree with it.
- Shadow runs the full classification and prices the result without moving a byte. Dry run copies a 1% stratified sample to scratch space and never commits, to measure real request cost and throughput.
- Rings are fractions of eligible objects selected by a stable hash, so the 1% ring contains the 0.1% ring and results compare across rings.
Gates between rings
- Re-read rate of demoted objects at most 1.5% within 14 days. Wrong-tier read rate at most 0.05%. Tiering charges at most 6% of gross saving; above 12% all demotion pauses.
- Realised bill delta within 20% of the shadow projection for the same population.
The cap that overrides rings
- No policy moves more than 2% of objects or 1.5 PB in any seven-day window. A tool that can relocate the corpus is a larger risk than the bill it exists to reduce.
