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help / color / mirror / Atom feedFrom: Christophe Pettus <[email protected]>
To: Laurenz Albe <[email protected]>
Cc: bruno vieira da silva <[email protected]>
Cc: [email protected]
Subject: Re: data checksums
Date: Tue, 6 Aug 2024 20:14:22 -0700
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CAB+Nuk8y88kvoRHsfN2Pjed9o_iM+9FbveU=4P8G0EQbzFP+qw@mail.gmail.com>
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> On Aug 6, 2024, at 19:45, Laurenz Albe <[email protected]> wrote:
> I am surprised by that. Would you say that most storage systems will happily give you a
> garbage block if there was a hardware problem somewhere?
"Most" is hard for me to judge. HDDs can have uncorrected and undetected errors, definitely. ZFS, for example, can correct those (within limits); XFS doesn't try. I have been told that SSDs can have uncorrected/undetected errors as well, but I don't know details on that.
> Turning data checksums on will write WAL for hint bits, which can significantly increase
> the amount of WAL written.
I was curious about that, so I just did a quick experiment using pgbench, with identical databases except for checksums. They both generated the same amount of WAL within 10% or so, so I don't think the impact is huge. (And you need the hint bits for pg_rewind, which is a nice thing to have in your back pocket if required.)
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