Backups aren't simple
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Data Loss & the Single Point of Failure:
- Data loss is an inevitable eventuality caused by hardware failure, bit rot (NAND transistor charge leakage or HDD magnetic drift), human mistakes, or UI issues (e.g., consumer devices prompting accidental disk formatting).
- Relying on a single storage drive or device is fundamentally unsafe.
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RAID vs. True Backups:
- RAID 1 / disk mirroring provides uptime redundancy against immediate drive death, but it is not a backup.
- Mirroring propagates accidental deletions, script mistakes, and ransomware encryption instantly across disks; point-in-time snapshots are mandatory to roll back changes.
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Retention, RPO, and Backup Rotation:
- Recovery Point Objective (RPO) dictates snapshot frequency, varying from under 30 seconds for critical infrastructure to 24+ hours for small workloads.
- Unpruned snapshots quickly exhaust storage, requiring structured rotation schemes such as Grandfather-Father-Son (GFS) to retain dense recent snapshots and sparser older ones.
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Deduplication and Storage Optimization:
- File changes follow a fat-tailed distribution, where most files remain static while a small fraction change frequently.
- Deduplicating identical files across snapshots (e.g., using hard links with tools like
rsnapshotor chunk-level deduplication) drastically reduces local storage usage and network bandwidth costs.
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Technical Pitfalls of DIY Backup Systems:
- Permissions & Containers: Background cron jobs running under standard user accounts fail on root-owned Docker files and volumes.
- State Consistency: Live databases caching writes in-memory risk silent corruption if snapshotted without explicit database dumps or I/O freezing.
- Cloud Object Storage (S3): Storing millions of small, unbundled files causes punitive API request costs and strips POSIX file metadata, requiring custom archive packaging or chunking.
- Daylight Saving Time (DST): Backup cron jobs scheduled between 2:00 AM and 3:00 AM can be skipped or executed twice during clock shifts.
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The 3-2-1 Rule and Battle-Tested Tooling:
- Resilient backup architecture requires the 3-2-1 strategy: 3 copies of data, across 2 different media types, with at least 1 offsite.
- Due to hidden edge cases, custom backup scripts should be avoided in favor of mature, open-source solutions (e.g., Borg, Restic, or ZFS snapshots) that provide chunk deduplication, checksum verification, and encryption out of the box.
- Backups are meaningless without regularly scheduled restore testing.
Hacker News Discussion
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Backups as High-Risk Operations:
- Several users noted experiencing catastrophic data loss during backup routines due to errant scripts wiping source data or premature deletion of old backups to make room for new ones.
- Commenters emphasized keeping at least one backup volume strictly offline and disconnected while running backup or rotation tasks.
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Cloud Vendor & Synchronization Pitfalls:
- Real-world horror stories highlighted sudden vendor policy shifts (e.g., Microsoft OneDrive or cloud providers altering storage tiers, aggressively throttling retrieval speeds, or silently purging files).
- Sync-based cloud tools frequently conflict with underlying filesystems and give users a false sense of backup security.
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Append-Only & Immutability Guarantees:
- To counter ransomware and compromised backup credentials, users advocated for provider-enforced immutability (such as S3 Object Lock) where backup keys have append-only privileges and cannot delete or overwrite historical objects.
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Physical Media & Cold Storage:
- Participants discussed hardware longevity trade-offs, noting the decline of optical media (Blu-ray burners) and highlighting used LTO tape drives (e.g., affordable LTO-5 units) as practical options for multi-terabyte cold offline archives.
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Walled Gardens and Cloud Photos:
- Backing up services like iCloud Photos or Google Photos remains difficult due to proprietary metadata handling, rate limits, and missing bulk export tools.
- Common community workarounds include running open-source sync tools (such as
icloud_photos_downloader), local Mac/Time Machine caching, or migrating to self-hosted photo platforms like Immich backed up to remote storage boxes.
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Filesystem & Application Consistency:
- Commenters highlighted the need for consistency groups and file system snapshots (such as ZFS or Btrfs) to freeze application I/O, preserve extended attributes/ACLs, and handle sparse virtual machine disk images properly.








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