Re: consistent postgresql snapshot

On 5/11/22 10:41, Zwettler Markus (OIZ) wrote:

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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();"