A disk so full, it couldn't be restored

Original Article ↗ Hacker News Discussion ↗

APFS / macOS behavior with full disks

  • Multiple users report APFS volumes becoming effectively bricked when near‑100% full: rm and GUI deletion fail with “No space left on device,” even from Recovery OS.
  • The likely cause discussed: copy‑on‑write and journaling need free space for metadata/log updates; if that pool is exhausted, even deletions or truncations may fail.
  • Some say APFS is more fragile in this state than HFS+ was; others note similar issues historically with ZFS and Btrfs, which now reserve “slop space” to avoid this.
  • Several note this can also hit iPhones/iOS, causing boot loops or requiring DFU restore when storage is maxed.

Workarounds and recovery techniques

  • Suggested tactics:
    • Boot into Recovery or single‑user mode, run fsck/Disk Utility repairs on the “Data” volume, then delete large files.
    • Truncate large files instead of deleting (various shell idioms: >file, truncate -s0, :>file), though some report even truncation failing on APFS.
    • Delete APFS/Time Machine local snapshots with tmutil, or APFS snapshots via Disk Utility.
    • Clone the disk to a larger one, expand, then clean up.
    • In extreme cases: reformat and restore from backup.
  • Some describe using placeholder “ballast” files to instantly free space when a disk gets dangerously full.

Time Machine reliability and alternatives

  • Opinions are sharply divided:
    • Many describe Time Machine as chronically unreliable: sparsebundles corrupting, network restores broken (especially over SMB on recent macOS), and Time Machine volumes hard to copy or migrate.
    • Others report long‑term success over many years, especially with local SSD targets.
  • Several suggest alternatives: Backblaze (with caveats about its encryption model), Arq with cloud storage (e.g., S3/Glacier), or open‑source tools (restic/borg/kopia, rsync+ssh, ZFS).

Apple ecosystem and quality concerns

  • Commenters criticize Apple for:
    • Not preventing full‑disk states from wedging the system.
    • Declining macOS quality, especially around networking (SMB), filesystem robustness, and Sonoma regressions.
    • Pushing users toward iCloud instead of investing in robust local backup/restore.
  • Others counter that macOS and Time Machine still compare favorably to Windows or remain “good enough” for many users.