RE: Are ZFS snapshots unsafe when PGSQL is spreading through multiple zpools?

From: HECTOR INGERTO <hector_25e(at)hotmail(dot)com>
To: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, Magnus Hagander <magnus(at)hagander(dot)net>
Cc: "pgsql-general(at)postgresql(dot)org <pgsql-general(at)postgresql(dot)org>" <pgsql-general(at)postgresql(dot)org>
Subject: RE: Are ZFS snapshots unsafe when PGSQL is spreading through multiple zpools?
Date: 2023-01-17 15:22:02
Message-ID: GV1P189MB20363DCA2B387BB3E4B2643FF5C69@GV1P189MB2036.EURP189.PROD.OUTLOOK.COM
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> Another case: a transaction COMMITs, and a slightly later transaction reads the data
> and sets a hint bit. If the snapshot of the file system with the data directory in it
> is slightly later than the snapshot of the file system with "pg_wal", the COMMIT might
> not be part of the snapshot, but the hint bit could be.
>
> Then these uncommitted data could be visible if you recover from the snapshot.
>
> Yours,
> Laurenz Albe

Thank you all. I have it clearer now.

As a last point. Making the snapshot to the WAL dataset first or last would make any difference?

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