4 ms·
With fsync_always it's crash safe for all but the most pathological scenarios.
by dallbee 7y ago
With fsync_always it's crash safe for all but the most pathological scenarios.
- TylerE 7y agoHow? It's persisting to a RAM disk. It only properly cleans up when sent a specific shutdown signal.
- dallbee 7y agoSorry fsync_always is a redis setting, not memcached. The fsync is to a real disk. The parent poster's comment about redis being crash safe to 1s is just the default.
- deleted 7y ago[deleted]
- gokhan 7y agoBut it's performance is way worst, almost voiding the case for choosing Redis.
- RhodesianHunter 7y agoI have not found this to be true. I suppose it depends on your use case and deployment.
- tus88 7y agoI do wonder what happens when a process writes to a memory mapped file, but crashes before the page is synced to disk. Does the write disappear?
- antirez 7y agoIf the OS is still alive, everything is ok (but the OS may sync different pages at different times and in any order if you don't fsync specific ranges with special calls). If the whole machine crashes (power issue, kernel panic, ...), what you find on disk can be a mess.
- derefr 7y ago> what you find on disk can be a mess Is this "can be" determined by the backing filesystem? E.g., would you expect to get a clean result from a log-structured or copy-on-write filesystem?