Are You Sure You Want to Use MMAP in Your Database Management System?

Re:Are You Sure You Want to Use MMAP in Your Database Manage... by jandrewrogers on Sunday July 02, 2023 @10:49PM (#36568154)

> You don't need more than single-writer concurrency if your write txns are fast enough.

This only works on systems with sufficiently slow storage. If your server has a bunch of NVMe, which is a pretty normal database config these days, you will be hard-pressed to get anywhere close to the theoretical throughput of the storage with a single writer. That requires 10+ GB/s sustained. It is a piece of cake with multiple writers and a good architecture.

Writes through indexing can be sustained at this rate (assuming appropriate data structures), most of the technical challenge is driving the network at the necessary rate in my experience.

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Re:Are You Sure You Want to Use MMAP in Your Database Manage... by hyc_symas on Monday July 03, 2023 @04:34AM (#36570312)

That's all just false. Just because you're single-writer at the application level doesn't mean the OS isn't queueing enough writes to saturate storage at the device level. We've benchmarked plenty of high speed NVMe devices, like Intel Optane SSDs, etc. showing this. http://www.lmdb.tech/bench/optanessd/

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Re:Are You Sure You Want to Use MMAP in Your Database Manage... by heisjustsosmart on Wednesday July 05, 2023 @01:39PM (#36603955)

this guy is a fool. Ignore him. Or see his website.

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