FSx File System -- Review Storage Tier
What does ZopNight detect here?
FSx for Windows and Lustre file systems on SSD storage often over-pay when workloads need modest IOPS. Windows Single-AZ SSD runs $0.130 per GB-month versus $0.013 on HDD. ZopNight prices the swap as the real rate delta times capacity times 730 hours, abstaining on OpenZFS and NetApp ONTAP, which are SSD-only.
Signal and threshold
| Field | Value |
|---|---|
| Rule IDs | RC-195 |
| Category | rightsizing |
| Severity | low |
| Metric | none — pure configuration read |
| Source | fsx_optimization.go |
Where it applies
Which FSx types can hold HDD storage
- Metadata[“storageType”] == “SSD” (discoverer FSxProvider, DescribeFileSystems; the prior hasTag(Tags,“storage_type”/“throughput_low”) gates were dead TAG_GATED_DEAD reads)
- Metadata[“fileSystemType”] ∈ {WINDOWS, LUSTRE}, since HDD is supported only on these; OpenZFS / NetApp ONTAP are SSD-only, so an SSD→HDD swap is impossible there → abstain
- PricingAware (context-first, legacy map fallback): per-resource monthly cost
- resource.SizeGB (discoverer FSx StorageCapacity, GB), required to price the direct storage-tier delta; abstains when ≤0
- SKURatesAware + TargetSKUCandidates: fsx-ssd (source) + fsx-hdd (target) catalog rates (the no-op SetSKURates exists only to flip HasSKURatesAware(“aws”,“fsx”) true so the service seeds these rates)
Why the SSD to HDD delta skips the shared helper
concrete-or-abstain (cost-driven rightsizing; the prior “performance”/SavingsUSD=0 advisory dodge is removed). savings = (fsx-ssd rate − fsx-hdd rate) × resource.SizeGB × 730, capped at the per-resource cost (savings ≤ cost invariant). This is a direct rate-delta computation, not model.DeriveCatalogDiffSavings, because that helper’s compute-calibrated magnitude floor (0.001/hr) and fraction ceiling (0.85) both incorrectly reject a real FSx storage swap: the aggregator prorates FSx catalog storage rates to $/GB-hour at ingest (÷730), so real srcRate/dstRate are ~1e-4/1e-5 (always below the 0.001 floor), and the real AWS delta (Windows Single-AZ SSD $0.130 vs HDD $0.013/GB-mo, both taken from the published FSx storage rates) is ~0.90, above the 0.85 ceiling. Abstains (returns nil) whenever either rate is missing/non-positive, the HDD rate is not cheaper, or SizeGB is ≤0. Never a fabricated fraction, never SavingsUSD=0 under the cost-driven category.
Migrating to an HDD file system
- Review the CloudWatch metrics FSx publishes per file system for IOPS and throughput patterns
- If IOPS requirements are low, create a new file system with HDD storage
- Migrate data using DataSync or rsync
- Update mount targets in applications