SSDs Have Become Fast, Except in the Cloud

Re:SSDs Have Become Fast, Except in the Cloud by scottlamb on Wednesday February 21, 2024 @01:18PM (#39457390)

Thanks for the link. How does this compare to the analogous situation for SSD access? I know there are also userspace IO stacks for similar reasons, but it seems like SSD-via-kernel is way ahead of network-via-kernel in the sense that it adds less latency per operation over the best userspace stack.

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Re:SSDs Have Become Fast, Except in the Cloud by vitus on Wednesday February 21, 2024 @06:56PM (#39461329)

I can't say offhand, since I don't have much experience with storage.

I'd expect that most of the work from a SSD read is offloaded to the disk controller, which presumably uses DMA, and you don't have nearly as many round trips (a sequential read can be done with a single SCSI command).

I'm inclined to agree with the explanation given by other commenters that the limiting factor for SSD r/w speeds in the cloud is due to throttling in the hypervisor to provide users with predictable performance as well as isolation in a multitenant environment.

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