Because even if you can squeeze 100TB or more of SSD/NVMe in a server, and there are 10 tenants using the machine, you're limited to 10TB as a hard ceiling.
What happens when one tenant needs 200TB attached to a server?
Cloud providers are starting to offer local SSD/NVMe, but you're renting the entire machine, and you're still limited to exactly what's installed in that server.
Given AWS and GCP offer multiple sizes for the same processor version with local SSDs, I don't think you have to rent the entire machine.
Search for i3en API names and you'll see:
i3en.large, 2x CPU, 1250GB SSD
i3en.xlarge, 4x CPU, 2500GB SSD
i3en.2xlarge, 8x CPU, 2x2500GB SSD
i3en.3xlarge, 12x CPU, 7500GB SSD
i3en.6xlarge, 24x CPU, 2x7500GB SSD
i3en.12xlarge, 48x CPU, 4x7500GB SSD
i3en.24xlarge, 96x CPU, 8x7500GB SSD
i3en.metal, 96x CPU, 8x7500GB SSD
So they've got servers with 96 CPUs and 8x7500GB SSDs. You can get a slice of one, or you can get the whole one. All of these are the ratio of 625GB of local SSD per CPU core.
> What happens when one tenant needs 200TB attached to a server?
Link to this mythical hosting service that expects far less than 200TB of data per client but just pulls a sad face and takes the extra cost on board when a client demands it. :D
It isn't. You could ask for network-attached CPUs or RAM. You'd be the only one, though, so in practice only network-attached storage makes sense business-wise. It also makes sense if you need to provision larger-than-usual amounts like tens of TB - these are usually hard to come by in a single server, but quite mundane for storage appliances.
Because a fair number of customers spin up another image when cores/mem/bandwidth run low. Dedicated storage breaks that paradigm.
Also, adding, if I am on an 8 core machine and need 16, network storage can be detached from host A and connected to host B. In dedicated storage it must be fully copied over first.
What happens when one tenant needs 200TB attached to a server?
Cloud providers are starting to offer local SSD/NVMe, but you're renting the entire machine, and you're still limited to exactly what's installed in that server.