From fb410259c58e68b327a48feba4810e4cf8971971 Mon Sep 17 00:00:00 2001 From: Julien Lutran Date: Tue, 25 Aug 2026 12:44:48 +0200 Subject: [PATCH] =?UTF-8?q?restic-backup:=20restic=20becomes=20THE=20S3=20?= =?UTF-8?q?tool=20=E2=80=94=20full=20rewrite?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Four buckets (data/nextcloud/seafile/instances), instances leg via incus file mount (no plugin architecture in restic/rustic — mount the source instead of forking the tool), nightly driver spec, parallel plakar comparison week, plakar retirement plan (kloset kept for PlakarKorp/plakar#2338 debugging), interim ks2 replica push until the FTTH/nuc leg. Co-Authored-By: Claude Fable 5 --- ks4/restic-backup.md | 325 ++++++++++++++++++++++--------------------- 1 file changed, 166 insertions(+), 159 deletions(-) diff --git a/ks4/restic-backup.md b/ks4/restic-backup.md index 72e4117..9f146c6 100644 --- a/ks4/restic-backup.md +++ b/ks4/restic-backup.md @@ -1,43 +1,40 @@ -# restic backups on ks4 — the giant fs trees +# restic backups on ks4 — the S3 leg -Status: **drafted 2026-08-25, not yet deployed.** +Status: **decided 2026-08-25 — restic replaces plakar as the S3 +backup tool** (evaluation first: parallel run + comparison, see §8). +Final architecture: **two tools** — `incus copy` for replication +(local sdb, nuc after FTTH, ks2 push as interim), **restic** for +everything S3. -Why restic exists in this stack: plakar's incremental cost scales -with tree size, not churn (~800 MiB of parent metadata re-read from -S3 + hours of CPU per night on a 500k-file tree — measured, reported -as [PlakarKorp/plakar#2338](https://github.com/PlakarKorp/plakar/issues/2338)), -which priced `nextcloud-fs` and `seafile-fs` out of the plakar data -leg. restic keeps its comparison state in a **local cache**, so a -night costs a local stat-walk plus the churn — the rsync cost model. -plakar keeps everything it is good at (dumps, small sources, small -instances); restic covers only the two giants until #2338 is -resolved (see §7). +Why: plakar's incremental cost scales with tree size, not churn +(~800 MiB parent metadata re-read from S3 + hours of CPU per night on +a 500k-file tree — measured, reported as +[PlakarKorp/plakar#2338](https://github.com/PlakarKorp/plakar/issues/2338)). +restic keeps its comparison state in a local cache: a night costs a +local stat-walk plus the churn — the rsync cost model. Neither restic +nor rustic has plakar's source-plugin architecture, but none is +needed: instances are reached via `incus file mount` (FUSE over the +same per-instance sftp API our plakar integration used) — zero +patches to maintain (see §6). -Scope: +## 1. Repositories — one bucket per repo -| source | size | files | churn/night (measured) | +| bucket = repo | contents | est. size | blobs (index RAM driver) | |---|---|---|---| -| `/nextcloud` (live, nextcloud container) | 737 G | ~500 k | 90–430 MiB | -| `/opt/seafile` (live, seafile container) | 933 G | millions of ~100 KiB block files | append-mostly | +| `restic-data` | `/backup/plakar-dumps` dump tree + the 8 small fs sources | ~50 G | small | +| `restic-nextcloud` | `/nextcloud` data (live rootfs path) | 737 G | ~1 M | +| `restic-seafile` | `/opt/seafile` (live rootfs path) | 933 G | ~2–4 M | +| `restic-instances` | the `backup`-project replicas, per-file via mount | ~16 small instances | medium | -Read from the live rootfs paths on the host (crash-consistent, like -the plakar fs sources; DBs are covered by the dump leg). +Separate repos because restic loads the whole repo index into RAM per +operation and prune/check are per-repo; separate **buckets** (not +prefixes) for per-bucket OVH usage metrics, independent +versioning/object-lock decisions later, and bucket-native credential +scoping. One credential pair across all four to start. -## 1. Repository layout — one bucket, two repos - -Two **separate repositories** under one bucket -(`s3:s3.sbg.io.cloud.ovh.net/restic/nextcloud` and `.../restic/seafile`): - -- restic loads the whole repo index into RAM per operation; the two - datasets share no content, so a shared repo only inflates every - run's memory for zero dedup gain. -- prune/check run per repo — seafile's heavy maintenance never blocks - or bloats nextcloud's. -- one bucket keeps credential handling identical to the plakar legs. - -Same passphrase discipline as plakar: generate to -`/root/.restic-passphrase` (mode 600), **copy to the password manager -immediately**. +Passphrase: `/root/.restic-passphrase` (mode 600), one for all repos, +**copy to the password manager immediately**. S3 creds + env in +`/root/.restic-env` (mode 600). ## 2. Option analysis (our numbers, not defaults-worship) @@ -52,45 +49,38 @@ amplification: |---|---|---| | 16 MiB | ~75 000 | slow `check`/listing, more requests; prune rewrites are fine-grained | | **64 MiB (chosen)** | ~19 000 | 4× fewer objects/requests; assembly RAM ≈ pack×connections ≈ 64 M × 5 ≈ 320 MiB — fine | -| 128 MiB | ~9 500 | fewer still, but prune rewrite amplification doubles (a pack with one dead blob rewrites 128 MiB) and upload buffers grow | +| 128 MiB | ~9 500 | fewer still, but prune rewrite amplification doubles and upload buffers grow | -`--pack-size 64` on **every backup/prune invocation** (it is not a -repo property). +`--pack-size 64` on **every backup/prune invocation** (not a repo +property). ### Memory (the real constraint on this 23/31 GiB-used box) -- Index RAM ≈ 200–300 B/blob. Estimate: nextcloud ~1 M blobs, - seafile ~2–4 M (tiny files = ≥1 blob each) → **~0.3 GiB and - ~0.6–1.2 GiB** respectively per backup run; prune peaks 2–3×. - This is why the repos are split (§1). -- `GOGC=20` env trades CPU for a substantially smaller Go heap — - enable it if the seafile prune ever pressures the box. +- Index RAM ≈ 200–300 B/blob → ~0.3 GiB (nextcloud) and + ~0.6–1.2 GiB (seafile) per backup run; prune peaks 2–3×. Hence the + repo split (§1). +- `GOGC=20` trades CPU for a smaller Go heap — enable if the seafile + prune ever pressures the box. ### Cache location `~/.cache/restic` would land on `/` (14 G free) and can reach a few -GiB for repos this size → `--cache-dir /backup/restic-cache` (sdb -pool, plenty of room; cache reads are small but ARC-warm after first -use). +GiB at this scale → `--cache-dir /backup/restic-cache` (sdb pool; +cache reads are ARC-warm after first touch). tmpfs was considered and +rejected: the cache exists to avoid *network* metadata re-fetches; +tmpfs loses it at reboot and eats the RAM the ARC needs. -### Concurrency +### Concurrency & compression - `--read-concurrency 8` (default 2): more outstanding reads lets the - HDD elevator help on the seek-bound seafile tree — the one knob that - directly targets our 275-IOPS wall. -- `-o s3.connections=8` (default 5): mild upload parallelism bump; - OVH same-region sustains it. - -### Compression - -Repo format v2 default `auto` is right; `max` only buys ~% on -already-compressed content (seafile blocks, images) for real CPU. + HDD elevator help on seek-bound trees (our 275-IOPS wall). +- `-o s3.connections=8` (default 5): mild upload parallelism bump. +- Compression: repo-v2 default `auto` is right. ### Excludes — the cheapest optimisation of all Nextcloud's `appdata_*/preview` (and `dav-photocache`) are -**regenerable caches holding a large fraction of the 500k files**; -excluding them shrinks walk and churn dramatically: +regenerable caches holding a large fraction of the 500k files: ``` # /root/scripts/restic-nextcloud-exclude @@ -98,143 +88,160 @@ excluding them shrinks walk and churn dramatically: /var/lib/incus/storage-pools/data/containers/nextcloud/rootfs/nextcloud/data/appdata_*/dav-photocache ``` -Seafile: no excludes — the block store *is* the data. - -Verify excludes before the seed: count the win with -`find .../appdata_* -path '*/preview/*' | wc -l`, then -`restic backup --dry-run -vv --exclude-file ...` prints every -include/exclude decision without uploading. (Per-user `/cache/` -dirs are a further regenerable candidate if the count justifies it.) - -Cache on tmpfs was considered and rejected: the cache exists to avoid -*network* metadata re-fetches; tmpfs loses it at reboot (forcing a -full re-download), eats the RAM the ARC needs, and buys nothing — -disk-backed cache reads are ARC-warm after first touch anyway. +Verify before the seed: `find .../data/appdata_* -path '*/preview/*' | wc -l` +for the win size, then `restic backup --dry-run -vv --exclude-file …` +prints every decision without uploading. Per-user `/cache/` +dirs are a further candidate. Seafile: no excludes — the block store +*is* the data. ### Escape hatch: rustic -[rustic](https://github.com/rustic-rs/rustic) speaks the **same -repository format** — switching later is a binary swap on the same -repos, no re-seed. It would solve two specific pains if they -materialize: **lock-free prune** (no backup/prune scheduling -constraint) and a **lower RAM footprint** (the seafile-index -concern). Not chosen first because it isn't in Debian (manual -upgrades) and has a far smaller community than restic. Don't run -both tools concurrently on one repo (rustic ignores restic's locks); -a clean switchover is fine. +[rustic](https://github.com/rustic-rs/rustic) speaks the same +repository format — switching later is a binary swap on the same +repos (decided 2026-08-25: restic first, rustic if performance +issues rise; manual upgrades accepted). It would bring lock-free +prune and a lower RAM footprint. Don't run both concurrently on one +repo (rustic ignores restic's locks); a clean switchover is fine. ## 3. Install + init (root on ks4) ```sh -apt install restic # Debian 13 ships ≥0.17 (repo v2, compression, pack-size ok) +apt install restic sshfs # sshfs: needed by `incus file mount` (§6) head -c 32 /dev/urandom | base64 > /root/.restic-passphrase && chmod 600 /root/.restic-passphrase # ⚠️ password manager, NOW. -export AWS_ACCESS_KEY_ID= AWS_SECRET_ACCESS_KEY= # -> /root/.restic-env (mode 600) +cat > /root/.restic-env <<'EOF' +export AWS_ACCESS_KEY_ID= +export AWS_SECRET_ACCESS_KEY= export RESTIC_PASSWORD_FILE=/root/.restic-passphrase -restic -r s3:s3.sbg.io.cloud.ovh.net/restic/nextcloud init -restic -r s3:s3.sbg.io.cloud.ovh.net/restic/seafile init -mkdir -p /backup/restic-cache +export RESTIC_CACHE_DIR=/backup/restic-cache +EOF +chmod 600 /root/.restic-env && . /root/.restic-env && mkdir -p /backup/restic-cache + +for r in restic-data restic-nextcloud restic-seafile restic-instances; do + restic -r s3:s3.sbg.io.cloud.ovh.net/$r init +done ``` ## 4. Seed plan -Order matters: - -1. **Bump the ARC floor first** so metadata walks stay warm between - nightly runs (also helps the plakar legs): +1. **ARC floor first** (helps every walk on the box): ```sh echo 8589934592 > /sys/module/zfs/parameters/zfs_arc_min echo "options zfs zfs_arc_min=8589934592" > /etc/modprobe.d/zfs-arc.conf - update-initramfs -u # zfs loads from the initramfs + update-initramfs -u awk '/^c_min/ {printf "%.1f GiB\n", $3/1073741824}' /proc/spl/kstat/zfs/arcstats ``` - ⚠️ the floor is defended even under memory pressure — real - headroom becomes ~31G − services − 8G; revisit before adding any - fat new service. -2. **nextcloud** (proven ~22 MiB/s from the live pool → ~8 h), in a + ⚠️ the floor is defended even under pressure — real headroom is + ~31 G − services − 8 G; revisit before adding a fat service. +2. `restic-data` (~50 G — an hour). +3. `restic-nextcloud` (proven ~22 MiB/s from the live pool → ~8 h), screen: ```sh - restic -r s3:.../restic/nextcloud --cache-dir /backup/restic-cache \ + restic -r s3:s3.sbg.io.cloud.ovh.net/restic-nextcloud \ backup --pack-size 64 --read-concurrency 8 -o s3.connections=8 \ --exclude-file /root/scripts/restic-nextcloud-exclude \ /var/lib/incus/storage-pools/data/containers/nextcloud/rootfs/nextcloud ``` -3. **seafile** — the one-time debt. Expect 1–2 days on the live pool - (warmer than sdb, and `--read-concurrency 8` helps); it is - restartable at any point (committed packs dedup on retry). +4. `restic-instances` (16 small replicas via §6 — a few hours). +5. `restic-seafile` — the one-time debt: 1–2 days, restartable at any + point (committed packs dedup on retry). -## 5. Nightly runs + retention + verification +## 5. Nightly driver — `scripts/restic-backup.sh` -Cron (05:00 — after the 04:30 plakar leg's dump phase, sources don't -overlap; wrap in a `restic-backup.sh` with flock + env, same style as -the plakar drivers): +Same shape as the plakar drivers (flock, env, loud logging). Phases: + +1. **dumps** — lifted verbatim from `plakar-backup.sh`: incus DB + dumps + auto-discovered MariaDB/PostgreSQL (native and docker) + dumps into `/backup/plakar-dumps` (path kept), then + `restic -r …/restic-data backup` of the dump tree **and** the 8 + small source paths (one snapshot, paths from a list file). +2. **giants** — nextcloud (with excludes) and seafile into their + repos. +3. **instances** — §6 loop into `restic-instances`. +4. **retention** — per repo: `restic forget --keep-daily 14 + --keep-weekly 8 --keep-monthly 6` (instant without `--prune`). ```cron 0 5 * * * /root/scripts/restic-backup.sh >> /var/log/restic-backup.log 2>&1 ``` -Per repo, the script does: +Weekly maintenance (Sunday; prune takes an **exclusive lock** — never +overlap the 05:00 run): -```sh -restic backup --pack-size 64 --read-concurrency 8 ... # as in §4 -restic forget --keep-daily 14 --keep-weekly 8 --keep-monthly 6 -restic unlock 2>/dev/null # clear stale locks after crashes +```cron +0 14 * * 0 /root/scripts/restic-maintenance.sh >> /var/log/restic-maintenance.log 2>&1 ``` -- `forget` without `--prune` is instant; actual **prune runs weekly** - (Sunday, offset from plakar's check; prune takes an exclusive lock — - never overlap the 05:00 backups): +Per repo: `restic prune --max-unused 10% --max-repack-size 4G +--pack-size 64` — our dead-data rate is ~0.1–0.4 GiB/day against +~700 GiB repos (seafile append-mostly ≈ nothing dies), so 10 % +tolerated slack lets prune skip repacking for months, and the 4 G cap +bounds any single Sunday to ~10–15 min even after a mass deletion. +Then `restic check` (structure, cheap) + `check +--read-data-subset=1/52` rotating — full data verification of every +byte once a year, ~25 GiB read per week. + +## 6. Instances without a plugin — `incus file mount` + +Neither restic nor rustic accepts source plugins, and forking the +backup tool is the wrong place to carry a patch. Instead, incus +exposes any instance (including **stopped replicas**) as a FUSE mount +over the same per-instance sftp API the plakar integration used: + +```sh +mkdir -p /run/restic-incus +for inst in $(incus list --project backup -c n -f csv); do + case ",$EXCLUDE_INSTANCES," in *",$inst,"*) continue;; esac # nextcloud,seafile + incus config show "$inst" --project backup --expanded > "/backup/plakar-dumps/incus/$inst.yaml" + incus file mount "$inst/" /run/restic-incus --project backup & # foreground process; background + kill + MPID=$!; sleep 2 + restic -r s3:…/restic-instances backup --pack-size 64 --tag "$inst" /run/restic-incus + kill $MPID; wait $MPID 2>/dev/null; umount /run/restic-incus 2>/dev/null +done +``` + +(Exact mount lifecycle to be hardened in the script — `incus file +mount` runs in the foreground and needs `sshfs` installed.) All +instances by default, opt-out via a variable — the no-manifest-drift +rule survives the tool change. Chained after the 01:00 incus-copy in +its cron entry once validated, same freshness reasoning as before. + +Bonus over plakar: one shared repo dedups the Ubuntu base across all +16 replicas. Restore granularity: per-file; instance definitions ride +the dump tree (`incus/.yaml` + `incus-global-db.sql`). + +## 7. Restore test (gate) + +Per repo, one restore + diff (never to `/tmp` — 16 GiB tmpfs): + +```sh +restic -r s3:…/restic-nextcloud restore latest --target /backup/restore-test --include '' +diff -r … && rm -rf /backup/restore-test +``` + +## 8. Evaluation protocol + plakar retirement + +- **Parallel week**: plakar 04:30 cron keeps running untouched; + restic runs at 05:00 on the same data. Same nights, same churn → + direct comparison (wall, bytes read from store, bytes written, peak + RSS via `/usr/bin/time -v`) against plakar's measured table in + [plakar-s3-data.md](plakar-s3-data.md). Restore-speed compared on + the same 10 GiB dumps tree (plakar measured: 39 min). +- **Cutover** (after the comparison confirms + restore test passes): + drop the plakar 04:30 + Sunday-check crons; 01:00 becomes + `incus-copy ; restic instances phase` (or stays in the 05:00 run). + Update plan.md legs table. +- **plakar retirement, one exception**: keep plakar installed and + keep the `plakar-data` kloset until + [#2338](https://github.com/PlakarKorp/plakar/issues/2338) concludes + — the issue offers debug runs against that repository. Delete the + `plakar-incus` bucket immediately; `plakar-data` a few weeks later. + The `integration-incus` repo retires from production; optionally + still publish to PlakarKorp/hub as a community contribution. +- **Interim ks2 push** (until the nuc leg seeds after FTTH, expected + before end of September): re-enable the replica push so instances + keep an off-site copy meanwhile: ```cron - 0 14 * * 0 ... restic prune --max-unused 10% --max-repack-size 4G --pack-size 64 ... + 0 2 * * * /root/scripts/incus-copy.sh -d ks2 -m push >> /var/log/incus-copy.log 2>&1 ``` - Tuning rationale (our churn: ~0.1–0.4 GiB/day dead data vs ~700 GiB - repos, seafile append-mostly ≈ nothing dies): `--max-unused 10%` - lets prune skip repacking for months, carrying ≤10 % slack in cheap - object storage; `--max-repack-size 4G` bounds any single Sunday's - rewrite to ~10–15 min even after a mass deletion, deferring the - rest to following weeks. (`--repack-small` only matters for repos - with legacy sub-64 MiB packs — not us, we start at 64.) -- **Verification**: weekly `restic check` (structure only, cheap) + - `check --read-data-subset=1/52` rotating — a full data verification - of every byte once a year, ~25 GiB read per week, for free. - -Expected steady state: nightly = local stat-walk (minutes once ARC is -warm) + churn upload; no per-run S3 metadata storm — the exact -property #2338 is about. - -## 6. Restore test (gate before trusting it) - -```sh -restic -r s3:.../restic/nextcloud --cache-dir /backup/restic-cache \ - restore latest --target /backup/restore-test --include '/' -diff -r ... && rm -rf /backup/restore-test -``` - -Never restore to `/tmp` — it is a 16 GiB tmpfs on ks4. - -## 7. If restic ever takes over ALL the S3 backups - -Decision gate: **the upstream answer to #2338.** Two futures: - -- **plakar fixes the growth problem** → consolidate the giants *back* - onto plakar, retire restic (delete the `restic` bucket) — one tool, - and the incus integration investment keeps compounding. -- **No fix on a useful horizon** → migrate the data leg to restic: - - dumps + 8 small fs sources are ~50 G total: re-seeding into a - `restic/data` repo is an evening, and restic dedups the nightly - dump tree (incl. the static `geo.sql`) exactly like plakar does. - - **the incus leg is the sticking point**: the per-file instance - backups ride our plakar-native integration. restic equivalents - are all worse or heavier: backing up replica rootfs paths - directly (fights incus's on-demand mounts), `incus export` - tarballs (server-side materialization, no room), or `zfs send` - streams into restic's stdin mode (works — `restic backup --stdin` - — but chains restore through zfs+incus knowledge). - - So a full migration really means "restic for all *file* data + - keep plakar only for the incus leg" — two tools either way. - Which is the same operational cost as today's split, minus the - #2338 exposure. Conclusion: **full migration buys little; the - current split is not a temporary hack but a reasonable end - state.** Revisit only if plakar becomes unmaintained or the - incus leg moves to zfs send anyway.