Re: consistent postgresql snapshot

On 5/11/22 10:41, Zwettler Markus (OIZ) wrote:
>
> PostgreSQL12 running on CentOS7 + ext4.
>
> Would it be save to do a "fsfreeze –freeze" + disk snapshot + "fsfreeze
> –unfreeze" of the PGDATA filesystem to get a consistent snapshot?
>
> I am wondering as PostgreSQL default blocksize = 8k while ext4 default
> blocksize = 4k, resulting in 2 fs blocks per db block.
>

If data/base and pg_xlog are on the same filesystem, then it might work.

Be sure to select pg_start_backup('something informative'); beforehand, and
select pg_stop_backup(); afterwards.

For example:
psql -c "select pg_start_backup('something informative');"
fsfreeze –freeze
/disk snapshot/
fsfreeze –unfreeze
psql -c "select pg_stop_backup();"

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