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SSDs have become fast, except in the cloud

(databasearchitects.blogspot.com)
589 points greghn | 1 comments | 20 Feb 24 16:59 UTC | HN request time: 0.223s | source
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pclmulqdq ◴[20 Feb 24 17:22 UTC] No.39443994[source]▶
This was a huge technical problem I worked on at Google, and is sort of fundamental to a cloud. I believe this is actually a big deal that drives peoples' technology directions.

SSDs in the cloud are attached over a network, and fundamentally have to be. The problem is that this network is so large and slow that it can't give you anywhere near the performance of a local SSD. This wasn't a problem for hard drives, which was the backing technology when a lot of these network attached storage systems were invented, because they are fundamentally slow compared to networks, but it is a problem for SSD.

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vlovich123 ◴[20 Feb 24 17:24 UTC] No.39444024[source]▶
Why do they fundamentally need to be network attached storage instead of local to the VM?
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pclmulqdq ◴[20 Feb 24 17:28 UTC] No.39444065[source]▶
Reliability. SSDs break and screw up a lot more frequently and more quickly than CPUs. Amazon has published a lot on the architecture of EBS, and they go through a good analysis of this. If you have a broken disk and you locally attach, you have a broken machine.

RAID helps you locally, but fundamentally relies on locality and low latency (and maybe custom hardware) to minimize the time window where you get true data corruption on a bad disk. That is insufficient for cloud storage.

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1. vlovich123 ◴[21 Feb 24 04:15 UTC] No.39450096[source]▶
Sure, but there's plenty of software that's written to use distributed unreliable storage similar to how cloud providers write their own software (e.g. Kafka). I can understand if many applications are just need something like EBS that's durable but looks like a normal disk, but not so sure it's a fundamentally required abstraction.