Abilio Marques wrote:
Hello,
I've successfully ported a particular piece of software from multiple plain files in disk to LMDB. There were multiple reasons to do so (i.e., performance and maintenance).
The program is making individual calls to a storage API, that in turn creates files or reads them (through a cache). There is no concept of transaction. For performance and lifetime reasons, the original code avoids to perform a fsync every time it writes to a file by queuing renames (for atomic writes) and deletes, which in turn are executed by a background thread after 2 seconds idling (or a max of 15 sec after first write/delete).
Replacing such a monster "files + cache" with LMDB was a breeze. I kept the API intact, and to deal with the price of fsyncs, I thought of opening with MDB_NOSYNC, and sync after 2 seconds of inactivity.
As documented, MDB_NOSYNC is only safe for power failure if the filesystem guarantees that it preserves the order of writes. Otherwise all bets are off.