So… it’s not durable? Durable doesn’t mean “survives a process restart”, it means “durably saved to persistent storage”. For example, this “durable” mode wouldn’t survive power loss.
stingraycharles 15 minutes ago [-]
Yeah this should be benchmarked against other systems that have flush() disabled.
mmap is nice but it doesn’t support durable semantics in the way that we usually mean with databases.
if a write is acknowledged it should not be forgotten, which is not what this is.
rgbimbochamp 2 minutes ago [-]
You're right, that mode provides process crash recovery, not power-loss durability. The benchmark compares it against fjall’s equivalent buffered-WAL mode.
nine_k 52 minutes ago [-]
I suppose the insane speed is due to this:
> TurboKV's persisted Bloom-filter format uses hardware AES.
Also, built-in LZ4 compression.
I would expect SIMD to be used for scans.
haberman 29 minutes ago [-]
I assume this is for hashing. I've seen several hashing algorithms turn to hardware AES instructions before, but I haven't seen any evidence that this technique outperforms state-of-the-art hashes like RapidHash (https://github.com/Nicoshev/rapidhash) in either quality or speed.
rgbimbochamp 50 minutes ago [-]
Those help but the main write speed gain is the WAL, that uses preallocated mmap segments to avoid a write(2) per durable mutation while preserving crash recovery.
AES hashing mainly helps Bloom filter point lookups and LZ4 mainly helps SSTable I/O. Scans benefit indirectly, but don’t yet use a custom SIMD merge loop.
dangoodmanUT 33 minutes ago [-]
Iirc that’s how badger handles the WAL as well
Rendered at 04:22:23 GMT+0000 (Coordinated Universal Time) with Vercel.
> Appended to the WAL without a per-write sync
So… it’s not durable? Durable doesn’t mean “survives a process restart”, it means “durably saved to persistent storage”. For example, this “durable” mode wouldn’t survive power loss.
mmap is nice but it doesn’t support durable semantics in the way that we usually mean with databases.
if a write is acknowledged it should not be forgotten, which is not what this is.
> TurboKV's persisted Bloom-filter format uses hardware AES.
Also, built-in LZ4 compression.
I would expect SIMD to be used for scans.