a) IO is such a large portion of the problem b) Hypertable isn't just way, way faster.
Their Java throughput is about 70% of their C++11 throughput, and that's with a pretty synthetic benchmark where there is not any logic behind those messages. Once you add in some real logic there, it gets even thinner.
They aren't doing user space networking, but that actually ought to allow Java to do even better.
Uh-huh... that's all pretty common for databases. Cassandra would fit that description.
> Never blocks on IO or page faults because all IO bypasses the kernel.
That just seems nonsensical. Sometimes, you are waiting for IO. That's just reality. It is conceivable you bypass the kernel for I/O, but that creates a lot of complexity and limitations. Near as I can tell though, they do talk to the kernel for IO.
Scylla never touches the page cache. All IO in seastar is direct IO and then scylla caches everything itself. We always know when the disk access is going to happen. The OS paging mechanism does not do a thing.
As for waiting for IO, of course IO does not complete immediately. But you can either block and wait for it, as Cassandra does (it doesn't even have the option not to in the case of the mmaped regions) or you can do something fully async like seastar that guarantees you never block waiting for IO.
By the way, I think you're replying to one of the devs of Scylla.
I'm very interested in a cluster benchmark therefor, say 10 servers, as Cassandra claims to scale very well. With a cluster IO has a higher performance impact than one server with local RAID IO.
