sprachspiel

Just tested a i4i.32xlarge:

  $ lsblk
  NAME         MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
  loop0          7:0    0  24.9M  1 loop /snap/amazon-ssm-agent/7628
  loop1          7:1    0  55.7M  1 loop /snap/core18/2812
  loop2          7:2    0  63.5M  1 loop /snap/core20/2015
  loop3          7:3    0 111.9M  1 loop /snap/lxd/24322
  loop4          7:4    0  40.9M  1 loop /snap/snapd/20290
  nvme0n1      259:0    0     8G  0 disk 
  ├─nvme0n1p1  259:1    0   7.9G  0 part /
  ├─nvme0n1p14 259:2    0     4M  0 part 
  └─nvme0n1p15 259:3    0   106M  0 part /boot/efi
  nvme2n1      259:4    0   3.4T  0 disk 
  nvme4n1      259:5    0   3.4T  0 disk 
  nvme1n1      259:6    0   3.4T  0 disk 
  nvme5n1      259:7    0   3.4T  0 disk 
  nvme7n1      259:8    0   3.4T  0 disk 
  nvme6n1      259:9    0   3.4T  0 disk 
  nvme3n1      259:10   0   3.4T  0 disk 
  nvme8n1      259:11   0   3.4T  0 disk

Since nvme0n1 is the EBS boot volume, we have 8 SSDs. And here's the read bandwidth for one of them:

  $ sudo fio --name=bla --filename=/dev/nvme2n1 --rw=read --iodepth=128 --ioengine=libaio --direct=1 --blocksize=16m
  bla: (g=0): rw=read, bs=(R) 16.0MiB-16.0MiB, (W) 16.0MiB-16.0MiB, (T) 16.0MiB-16.0MiB, ioengine=libaio, iodepth=128
  fio-3.28
  Starting 1 process
  ^Cbs: 1 (f=1): [R(1)][0.5%][r=2704MiB/s][r=169 IOPS][eta 20m:17s]

So we should have a total bandwidth of 2.7*8=21 GB/s. Not that great for 2024.

This is for 8 SSDs and a single modern PCIe 5.0 has better specs than this.

These settings control writing back modified pages. The experiments in the paper are read-only. With writes the situation is even worse than shown in the paper (though tuning these settings may help a bit).

This would be exactly the kind of innovation we would need in computer science. Instead we often get stuck in local minima (in this case a 40-year old POSIX interface) without realizing how much pain this causes.