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A comment on EC2 Instance Update – C5 Instances with Local NVMe Storage. Parent comment

Re:EC2 Instance Update – C5 Instances with Local NVMe Storage by ohre1Eda on Friday May 18, 2018 @04:55AM (#17099774)
I am curious, what kind of write characteristics can manage to saturate a 255s timeout on a storage device that does 10k+ iops and gigabytes per second throughput? Normally writes slowing down leads to backpressure because the syscalls issueing them take longer to return.

I can imagine some crazy random access, small-record, vectored IO from large thread pools. But that's not exactly common because most software that is IO-heavy tries really hard to avoid these things.

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Re:EC2 Instance Update – C5 Instances with Local NVMe Storage by lathiat on Friday May 18, 2018 @06:11AM (#17100187)
According to the bug here: https://bugs.launchpad.net/ubuntu/bionic/+source/linux/+bug/...

It was actually filed about EBS block disks using NVME (on these new instances, there is a hardware card that presents network EBS volumes as a PCI-E NVME device). In certain failure cases since this is a network block store, they can fail for some period of time exceeding this timeout.

The idea of this change is to ensure once they come back the machine is left in a usable state.

Of course, I would not expect to see this on Local NVME disks which is what they announced - that you can now get such instances with local disk as well as EBS.

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Re:EC2 Instance Update – C5 Instances with Local NVMe Storage by ohre1Eda on Friday May 18, 2018 @07:50AM (#17100648)
Ah yeah, the article was about local NVMe, so the concern is probably not relevant here.
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Re:EC2 Instance Update – C5 Instances with Local NVMe Storage by lathiat on Friday May 18, 2018 @11:23AM (#17102185)
Unrelated: love your pwgen username
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Re:EC2 Instance Update – C5 Instances with Local NVMe Storage by benmmurphy on Friday May 18, 2018 @07:20AM (#17100485)
EBS probably has really terrible tail latencies.
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