Date: Tue, 23 Mar 2021 19:07:20 +0100
From: Johannes Truschnigg <johannes@truschnigg.info>
To: Jerry Sievers <gsievers19@comcast.net>
Cc: pgsql-admin@postgresql.org
Subject: Re: Odd OS, SAN or related throughput issue affecting large streamer
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References: <87o8f9n5o0.fsf@jsievers.enova.com>
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Hi Jerry.

On Tue, Mar 23, 2021 at 12:25:35PM -0500, Jerry Sievers wrote:
> Greetings!
>=20
> [...]
> Suggestions re where to look next?

Have you looked at the usual OS-level metrics yet?

Does the process that applies the streamed WAL to the secondary's database
exhibit high CPU load when the slowdown starts becoming noticeable? Check by
using `top` and `mpstat`.

Does I/O latency spike/increase during that time? Maybe your system is
beginning to page data in and out? Check by using `iostat` and `vmstat`.

If you can identify a/the metric that changes when your troubles begin to
manifest, we should be able to help you drill down to the root cause of it =
all
much better.

--=20
with best regards:
- Johannes Truschnigg ( johannes@truschnigg.info )

www:   https://johannes.truschnigg.info/
phone: +43 650 2 133337
xmpp:  johannes@truschnigg.info

Please do not bother me with HTML-email or attachments. Thank you.

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