WAFL: Write Anywhere File Layout

Log-like write throughput

• No segment cleaning (LFS)
• Write data allocated to optimize RAID performance

  • Delayed write allocation

Active data is never overwritten (shadow paging)

• On-disk data is always consistent
• File system state is changed atomically

  • Every 10 sec, by default

Client modification requests are logged to NVRAM

• NVRAM log is replayed only on reboot

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