AOF Persistence Latency from Synchronous Disk Writes
warningWhen AOF persistence is enabled with appendfsync always or everysec, slow disk I/O can cause write latency spikes. redis.persistence.aof_last_rewrite_time_sec increasing significantly indicates AOF file growth without rewrite, amplifying disk I/O overhead.
Monitor redis.persistence.aof_enabled flag combined with redis.persistence.aof_current_size growing significantly between rewrites. Track redis.persistence.aof_last_rewrite_time_sec for baseline. Correlate with redis.commands.usec_per_call increases during write operations.
Tune auto-aof-rewrite-percentage and auto-aof-rewrite-min-size to trigger more frequent AOF rewrites before file grows too large. Consider switching from appendfsync always to everysec for better performance if occasional data loss is acceptable. Evaluate disk I/O performance and consider faster storage (SSDs) for Redis data directory. Monitor disk queue depth during AOF operations.