SSDs Have Become Fast, Except in the Cloud

Re:SSDs Have Become Fast, Except in the Cloud by barrkel on Wednesday February 21, 2024 @09:03AM (#39453911)

There's a quadrant of the market which is poorly served by the Cloud model of elastic compute: persistent local SSDs across shutdown and restart.

Elastic compute means you want to be able to treat compute hardware as fungible. Persistent local storage makes that a lot harder because the Cloud provider wants to hand out that compute to someone else after shutdown, so the local storage needs to be wiped.

So you either get ephemeral local SSDs (and have to handle rebuild on restart yourself) or network-attached SSDs with much higher reliability and persistence, but a fraction of the performance.

Active instances can be migrated, of course, with sufficient cleverness in the I/O stack.

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Re:SSDs Have Become Fast, Except in the Cloud by jsolson on Wednesday February 21, 2024 @11:42AM (#39456071)

GCE fares a little better than this:

- VMs with SSDs can (in general -- there are exceptions for things like GPUs and exceptionally large instances) live migrate with contents preserved.

- GCE supports a timeboxed "restart in place" feature where the VM stays in limbo ("REPAIRING") for some amount of time waiting for the host to return to service: https://cloud.google.com/compute/docs/instances/host-mainten.... This mostly only applies to transient failures like power-loss beyond battery/generator sustaining thresholds, software crashes, etc.

- There is a related feature, also controlled by the `--discard-local-ssd=` flag, which allows preservation of local SSD data on a customer initiated VM stop.

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