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Comment by rapsey

2 years ago

Because memcache and redis are in-memory. Writing to fdb will be complete once it is fsync'ed to disk.

Memcache is a cache. Fdb is a an ordered kv store.

Redis can be configured to persist and fsync every operation.

You can configure redis to flush to disk on write operations though you lose on performance.

  • That is not comparable to writes completing after they are flushed to disk.

    • >appendfsync always: fsync every time new commands are appended to the AOF. Very very slow, very safe. Note that the commands are appended to the AOF after a batch of commands from multiple clients or a pipeline are executed, so it means a single write and a single fsync (before sending the replies).

      https://redis.io/docs/management/persistence/

      It's very slow, but if you really want to wait for fsync before replying, it can do that.

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