Unlimited in this context just means you're going to be CPU limited before you hit limits on IOPS. It'd be technically not possible to be bottlenecked on IOPS.

That might not be 100% true, but I've never seen a RDBMS be able to saturate IOPS on a local NVMe. It's some quite specialized software to leverage every ounce of IOPS without being CPU bottlenecked first. Postgres and MySQL are not it.

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ndriscoll 3 days ago | parent [-]

What does "local NVMe" mean for you? AFAIK in AWS if you have a 2 core VM you're getting ~3% of a single disk worth of IOPS for their attached storage. Technically NVMe. Not generally what people think when a laptop can do 50x more IO. The minipc I mentioned has 4x the core count and... well who knows how much more IO capacity, but it seems like it should be able to trounce both. Obviously an even more interesting comparison would be... a real server. Why is a database company running benchmarks on something comparable to my low-end phone?

Anyway, saying unlimited is absurd. If you think it's more than you need, say how much it is and say that's more than you need. If you have infinite IOPS why not do the benchmark on a dataset that fits in CPU cache?

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mattrobenolt 3 days ago | parent | next [-]

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ssd-inst...

Not all AWS instance types support NVMe drives. It's not the same as normal attached storage.

I'm not really sure your arguments are in good faith here tho.

This is just not a configuration you can trivially do while maintaining durability and HA.

There's a lot of hype going the exact opposite direction and more separation of storage and compute. This is our counter to that. We think even EBS is bad.

This isn't a setup that is naturally just going to beat a "real server" that also has local NVMes or whatever you'd do yourself. This is just not what things like RDS or Aurora do, etc. Most things rely on EBS which is significantly worse than local storages. We aren't really claiming we've invented something new here. It's just unique in the managed database space.

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ndriscoll 3 days ago | parent [-]

Right, but as far as I know, the only instances that give you full bandwidth with NVMe drives are metal. Everything else gives you a proportional fraction based on VM size. So for most developers, yes it is hard to saturate an NVMe drive with e.g. 8-16 cores. Now how about the 100+ cores you actually need to rent to get that full bandwidth?

I agree that EBS and the defaults RDS tries to push you into are awful for a database in any case. 3k IOPS or something absurd like that. But that's kind of the point: AWS sells that as "SSD" storage. Sure it's SSD, but it's also 100-1000x slower than the SSDs most devs would think of. Their local "NVMe" is AFAIK also way slower than what it's meant to evoke in your mind unless you're getting the largest instances.

Actually, showing scaling behavior with large instances might make Planetscale look even better than competitors in AWS if you can scale further vertically before needing to go horizontal.

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mattrobenolt 3 days ago | parent [-]

Right, but I think you're kinda missing a lot of the tangible benefits here. This IMO is just reinforcing the idea of "unlimited" IOPS. You can't physically use the totality of IOPS available on the drives.

Even if you can't saturate them, even with low CPU cores, latency is drastically better which is highly important for database performance.

Having low latency is tangibly more important than throughput or number of IOPS once your dataset is larger than RAM no matter how many CPU cores you have.

Chasing down p95s and above really shine with NVMes purely from having whatever order of magnitude less latency.

Less latency also equates to less iowait time. All of this just leads to better CPU time utilization on your database.

	▲	ndriscoll 3 days ago \| parent [-]
		How does "AWS limits IOPS. 'NVMe' drives are not as fast as the drives you're used to unless you rent the biggest possible servers" reinforce "unlimited" IOPS? Yes there are benefits like lower latency, which is often measured in terms of qd1 IOPS.

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parthdesai 3 days ago | parent | prev [-]

They literally state this on their metal offering

> Unlimited I/O — Metal's local NVMe drives offer higher I/O bandwidth than network-attached storage. You will run out of CPU long before you use all your I/O bandwidth.

https://planetscale.com/metal#benefits-of-metal