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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: 0s | source
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siliconc0w ◴[20 Feb 24 17:23 UTC] No.39444011[source]▶
Core count plus modern nvme actually make a great case for moving away from the cloud- before it was, "your data probably fits into memory". These are so fast that they're close enough to memory so it's "your data surely fits on disk". This reduces the complexity of a lot of workloads so you can just buy a beefy server and do pretty insane caching/calculation/serving with just a single box or two for redundancy.
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malfist ◴[20 Feb 24 17:36 UTC] No.39444175[source]▶
I keep hearing that, but that's simply not true. SSDs are fast, but they're several orders of magnitude slower than RAM, which is orders of magnitude slower than CPU Cache.

Samsung 990 Pro 2TB has a latency of 40 μs

DDR4-2133 with a CAS 15 has a latency of 14 nano seconds.

DDR4 latency is 0.035% of one of the fastest SSDs, or to put it another way, DDR4 is 2,857x faster than an SSD.

L1 cache is typically accessible in 4 clock cycles, in 4.8 ghz cpu like the i7-10700, L1 cache latency is sub 1ns.

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1. Sweepi ◴[21 Feb 24 13:30 UTC] No.39453512[source]▶
To be pedantic because its fun:

The random access Latency for L1 is indeed ~4 cycles, but RAM is more like 70ns+ (so you are .5 order of magnitude off, how dare you?).

These are my notes from an Anandtech article:

  RAM:      
            5950x:         79 ns (400 cycles)
            3950x:         86 ns (400 cycles)
            10900k:        71 ns
            Apple M1:      97 ns
            Apple M1 Max: 111 ns
            Apple A15P:   105 ns
            Apple A15E:   141 ns
            Apple A14P:   101 ns
            Apple A14E:   201 ns
            888 X1:       114 ns
  L1 Cache: 
            5950x:        4 cycles (0.8 ns @ 5 GHz)
            Apple M1:     3 cycles
            Apple M1 Max: 3 cycles