Re: Performance issues during backup

Dylan Luong wrote:
> We perform nighty base backup of our production PostgreSQL instance. We have a script that basically puts the instance
> into back mode and then backs up (tar) the /Data directory and then takes it out of backup mode.
> Ie,
> psql -c "SELECT pg_start_backup('${DATE}');"
> tar -cvf - ${DATA_DIR} --exclude ${DATA_DIR}/pg_log | split -d -b $TAR_SPLIT_SIZE - ${BACKUP_DIR}/${BACKUP_NAME}
> psql -c "SELECT pg_stop_backup();"
>
> The size of our database is about 250GB and it usually takes about 1 hour to backup.
> During this time, we have performance issue where queries can take up to 15secs to return where normally it takes 2 to 3 seconds.
> During this time (1:30am) usage is low (less than 10 users) on the system.
>
> Has anyone experience the same problem and any suggestions where to look at to resolve the problem?

The "tar" is probably taking up too much I/O bandwidth.

Assuming this is Linux, you could run it with

ionice -c 2 -n 7 tar ...

or

ionice -c 3 tar ...

Of course then you can expect the backup to take more time.

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com