Configuring Persistence with AOF

1. Understanding AOF Concept

Property	Detail
Format	Append-only command log
Recovery	Replay log on restart
Durability	Tunable via fsync policy

2. Enabling AOF

Directive	Value
appendonly yes	Enable

3. Setting AOF Filename

Directive	Default
appenddirname	appendonlydir 7.0+
appendfilename	appendonly.aof (base name)

4. Configuring Fsync Policy

Policy	Durability	Performance
always	Per-write (max safety)	Slowest
everysec	≤1s loss (recommended)	Excellent
no	OS decides	Fastest

5. Rewriting AOF (BGREWRITEAOF)

Command	Description
BGREWRITEAOF	Compact AOF by writing minimal commands to reconstruct state

6. Auto-Rewrite Configuration

Directive	Default	Purpose
auto-aof-rewrite-percentage	100	Rewrite when AOF doubles vs last rewrite
auto-aof-rewrite-min-size	64mb	Min size to trigger rewrite

7. Enabling Mixed Persistence

Directive	Default	Effect
aof-use-rdb-preamble yes	yes	AOF starts with RDB snapshot + incremental commands — faster loads

8. Handling AOF Corruption

Tool	Description
redis-check-aof --fix	Truncate at corruption point
aof-load-truncated yes	Load partial AOF without manual fix

9. Understanding AOF vs RDB Tradeoffs

10. Managing AOF File Growth

Setting	Effect
auto-aof-rewrite-percentage	Lower → more frequent rewrites
Multi-part AOF	Manifest + base + incrementals 7.0+

11. Understanding Fsync Performance Impact

Policy	Latency Impact
always	Per-write fsync ≈ disk latency
everysec	Background thread, occasional spikes
no-appendfsync-on-rewrite yes	Skip fsync during rewrite

12. Recovering from AOF Files

Step	Action
1	Stop server
2	Verify with redis-check-aof
3	Place files in appenddirname
4	Start; replay happens automatically