From: | Christophe Pettus <xof(at)thebuild(dot)com> |
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To: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
Cc: | bruno vieira da silva <brunogiovs(at)gmail(dot)com>, pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | Re: data checksums |
Date: | 2024-08-07 03:14:22 |
Message-ID: | CB6A3572-FA73-4EA1-8BD5-F95739BC563C@thebuild.com |
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Lists: | pgsql-general |
> On Aug 6, 2024, at 19:45, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> 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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