55 lines
2.7 KiB
Markdown
55 lines
2.7 KiB
Markdown
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# PostgreSQL backup demand and cost model — 2026-08-10
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## Observed baseline
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A read-only query against `platform-pg-1` at `2026-08-10T15:54:12Z` measured
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39,573,871 bytes across connectable databases. `pg_stat_wal` reported
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19,744,568 bytes since `2026-08-10T13:37:53Z`, an extrapolated 0.208 GB/day.
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The cluster is less than one day old, so this is a seed observation rather than
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a representative trend. No credential value was read or recorded.
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The governed requirements are a 30-day recovery window, daily physical base
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backup, continuous WAL archive, one monthly restore drill, and a complete exit
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calculation. The scenario inputs live in
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`data/demand/platform-audit-storage.json` and deliberately floor demand above
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the tiny initial observation:
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| Scenario | Initial DB | Monthly growth | WAL/day | Restore egress | Labor/month |
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| --- | ---: | ---: | ---: | ---: | ---: |
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| low | 1 GB | 5% | 0.25 GB | 1 GB | 0.5 h |
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| base | 5 GB | 10% | 1 GB | 5 GB | 1 h |
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| high | 20 GB | 20% | 5 GB | 20 GB | 2 h |
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The conservative stored-byte formula is `30 × current database size + 30 ×
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daily WAL`. It does not claim compression savings. Operator labor is valued at
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€60/hour; provider-specific labor floors capture relative operational effort.
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The exit event adds full stored-byte egress plus four operator hours.
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Run `make forecast` for all 12 months, scenarios, and providers. A `null` total
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is intentional: it means a required price is unknown and prevents an unknown
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from silently becoming free.
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The catalog also includes self-managed Garage on 1–3 Host Europe/Hetzner VMs
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and managed AWS, Azure, Google Cloud, and STACKIT price points. See
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`RESOURCE-WP-0002-expanded-storage-comparison-2026-08-10.md` for assumptions
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and topology warnings.
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Calculator rows split `monthly_infrastructure_eur` from
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`monthly_internal_labor_eur` and split internal setup labor from external setup
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services. The top-level `comparison_320gb` array provides a normalized running
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cost at 320 GB using the base request and restore pattern.
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## Initial comparison
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- Scaleway Standard Multi-AZ is fully calculable at €0.01606/GB-month, with
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75 GB/month free egress then €0.01/GB. Prices exclude tax.
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- Hetzner is calculable while usage remains inside its €6.49 monthly minimum,
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which includes 1 TB storage and 1 TB egress. Excess unit prices still need to
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be captured before high-growth or exit usage crosses the included quota.
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- Host Europe cannot be calculated until it confirms that the historical S3
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Cloud Storage product is currently orderable and supplies a current quote.
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Because labor dominates this very small workload, selection should emphasize
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restore compatibility, independent failure domain, encryption, and exit proof
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before sub-euro storage differences.
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