add notes on storage architecture discussion

architecture-docs/2024-12-09 storage.md

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+# Storage architecture with Garage
+
+Attendees: Koen, Valentin, Nicolas
+
+* (some historical/technical background discussion on object storage and file systems)
+* Koen: 1.5 y ago looked into available FOSS solutions, only minio and Garage
+	* Garage was NGI-funded and located in France and responsive
+		* Targeted at self-hosting, minimal hardware requirements
+	* Ideally would have used a W3C standard protocol, but "S3-compatible" is the closest thing
+* Should have a few big, replicated, well-monitored storage clusters instead of many small ones
+	* Currently have 3x4Ux32drive storage boxes; would replicate them over 3 locations
+* (discussion of ZFS performance characteristics)
+* Koen presented a storage architecture based on ZFS
+	* Main feature (not clear on the details) is to add a NVMe-based primary write target to Garage
+		* e.g. 45TB NVMe + (2x?) 560 TB (1PB raw) HDD
+		* According to independent reviews[citation needed] Garage handles this sort of setup better than minio
+* Requirement estimates:
+	* mastodon.nl has 50k users, 5k active users, 200GB database (ever-growing, launched Nov 2022), 1.5 TB of files
+		* Hot data is <~5 days old, most of the rest is never looked up
+	* Most of the usage profiles intel will have to come from our university partners
+	* Will scale the physical storage to the actual write capacity requirements at the spindle layer (add more vdevs as needed)
+* Additional object storage replication can be configured at the S3 (Garage) layer by setting another target at a different provider
+	* We expect this to happen rarely; replication will likely take a lot of performance out of the application
+	* By default we already have 3-way replication internally (i.e. 3 RAIDZ2 machines per Garage instance)
+* There are already three sites in NL to rack the hardware
+	* This is why we need to connect NetherLight so NORDUnet universities have a low-latency connection
+* Koen: Ideally at the end of next year you'd have three sites set up with machines to run Proxmox on and the storage machines, and run a NixOS ISO to set everything up and then control it via NixPanel
+* Nicolas: We should talk to Garage developers, because they run it on NixOS but not sure how exactly
+	* Koen: Ideally before FOSDEM 2025
+* Valentin: Need reference documentation for the storage architecture discussed (so we can point to something when making implementation decisions), and a slide deck to tell the story of how it came into being (as a sales device for the project), and eventually derive business plans for hosting providers and operators from that
+
+Hand-drawn sketches posted to the internal private repo