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SSDs have become fast, except in the cloud

(databasearchitects.blogspot.com)
589 points greghn | 3 comments | 20 Feb 24 16:59 UTC | HN request time: 0.63s | 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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mkoubaa ◴[20 Feb 24 17:30 UTC] No.39444085[source]▶
Dumb question. Why does the network have to be slow? If the SSDs are two feet away from the motherboard and there's an optical connection to it, shouldn't it be fast? Are data centers putting SSDs super far away from motherboards?
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bugbuddy ◴[20 Feb 24 17:34 UTC] No.39444142[source]▶
> One theory is that EC2 intentionally caps the write speed at 1 GB/s to avoid frequent device failure, given the total number of writes per SSD is limited.

This is the theory that I would bet on because it lines up with their bottom line.

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1. Dylan16807 ◴[20 Feb 24 17:54 UTC] No.39444409[source]▶
But the sentence right after undermines it.

> However, this does not explain why the read bandwidth is stuck at 2 GB/s.

Faster read speeds would give them a more enticing product without wearing drives out.

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2. bugbuddy ◴[20 Feb 24 19:02 UTC] No.39445381[source]▶
They may be limiting the read artificially to increase your resource utilization else where. If you have disk bottleneck then you would be more likely to use more instances. It is still about the bottom line.
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3. Dylan16807 ◴[20 Feb 24 19:47 UTC] No.39445990[source]▶
That could be. But it's a completely different reason. If you summarize everything as "bottom line", you lose all the valuable information.