4 ms·

> In production, 10 metadata nodes each with 512 GB of memory collectively manage over 20 billion files. That doesn’t sound all that impressive—is it impressiv

• hansvm 3y ago
  They're only using 36% of that (so they have slack capacity). It's in-memory, which has some perf wins (though I'd question if distributed systems are worth it when you can get a PCIe splitter and just mmap some 4TB SSDs on whatever cheap desktop computer somebody has lying around). 100 bytes per file is less than you would expect to support all that data if you coded it "naturally" without an eye toward space efficiency. You'll need 16-32 bytes or so just to handle a tree structure with internal string indices to be able to support finding any given file's location quickly. Toss in created times, modified times, permissions, attributes, the fact that they have a chunking structure to support both random seek and efficient/easy allocation, .... It adds up to more than 100B if you're not pretty careful. They hit that 100B mark. Is that impressive? I dunno. Their competitors didn't do it, and they did, so that's something.