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0 pointshyc_symas13y ago0 comments

You're still not understanding. LMDB is a disk-based database. It is not only writing to memory.

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3 comments · 1 top-level

easytiger13y ago· 2 in thread

MDB in those stats is writing to disk? I assume its some kind of lazy write though where the memory store is eventually persisted? in that case thats fairly impressive for a lot of use cases. Though a k/v store has a lot less to do than something like sqlite3.

I'll look into it (never heard of it before). Might fix fairly well with something I'm working on right now (currently implemented using sqlite3).

hyc_symasOP13y ago

In fully synchronous mode, which is LMDB's default mode, everything is persisted upon commit. This is a memory-mapped database, not a main-memory/in-memory database. It is fully persistent to disk, it just so happens that it uses mmap() instead of read()/write() and a user-level page cache.

People are always confusing "memory-mapped" with "memory-only". LMDB is not a memory-only database.

http://www.openldap.org/lists/openldap-devel/201111/msg00064...

easytiger13y ago

I guess (as i did) assumed it meant memory-mapped I/O as opposed to something like memory-mapped file I/O or port mapping.

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