Re: AWS vs GCP storage

On Tue, Feb 22, 2022 at 12:27 PM Torsten Förtsch <tfoertsch123(at)gmail(dot)com>
wrote:

> Hi,
>
> I have a few databases with several TB-sized tables. We recently moved one
> of those databases from AWS EC2 to GCP. Today I ran VACUUM FREEZE on those
> tables and every time I saw our application freezing up (and throwing tons
> of errors) for a few minutes right after the message about the end of
> vacuum (duration: 30182257.392 ms statement: vacuum freeze verbose ...).
> We never saw anything like that on AWS.
>
> The database is 9.6. At the moment I have no details about the storage
> configuration on GCP. The machine was set up by another department.
>
> Any suggestions on why that is happening and how to prevent it would be
> appreciated.
>

The first thing to check is that you're using SSD PDs, not regular PDs.

Second: GCP has 2 rules for disk IO throttling (independent for regular PDs
and SSD PDs): based on disk size, and based on the number of vCPUs. You
need more vCPUs to get maximum disk IO, which may be counter-intuitive. I
suggest checking out the docs and benchmarking the disks using fio:
- https://cloud.google.com/compute/docs/disks/performance
- https://cloud.google.com/compute/docs/disks/benchmarking-pd-performance