That’s a lot of work creating a whole system that stores data on a raw block device. It would be nice to see this compared to… a filesystem. XFS, ZFS and btrfs are pretty popular.
> Despite serving from same-region datacenters 2 ms from the user, S3 would take 30-200 ms to respond to each request.
200ms seems fairly reasonable to me once we factor in all of the other aspects of S3. A lot of machines would have to die at Amazon for your data to become at risk.
> Direct I/O means no more fsync: no more complexity via background flushes and optimal scheduling of syncs. There's no kernel overhead from copying and coalescing. It essentially provides the performance, control, and simplicity of issuing raw 1:1 I/O requests.
Not true, you still need fsync in direct I/O to ensure durability in power loss situations. Some drives have write caches that means acknowledged writes live in non-volatile memory. So maybe the perf is wildly better because you’re sacrificing durability?
/// Even when using direct I/O, `fsync` is still necessary, as it ensures the device itself has flushed any internal caches.
async fn sync(&self) {
let (fut, fut_ctl) = SignalFuture::new();
self.sender.send(Request::Sync { res: fut_ctl }).unwrap();
fut.await
}
When you have a service and really care about shoving of S3 latencies in the millisecond range, then you propably have enough users that all the tiny images are cached @ edge anyways.
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[ 2.9 ms ] story [ 32.3 ms ] thread200ms seems fairly reasonable to me once we factor in all of the other aspects of S3. A lot of machines would have to die at Amazon for your data to become at risk.
Not true, you still need fsync in direct I/O to ensure durability in power loss situations. Some drives have write caches that means acknowledged writes live in non-volatile memory. So maybe the perf is wildly better because you’re sacrificing durability?
https://github.com/wilsonzlin/blobd/blob/master/libblobd-dir...