Thread

1. Pgbackrest info output interpretation

   KK CHN <kkchn.in@gmail.com> — 2025-11-14T08:32:38Z

   Hi,
   
   I am having confusion trying to understand the database size, backupsize
   and repo backup size..
   
   In my DB server I have du output as follows.
   
   /data/edb/as16
   [root@db1 as16]# du -h -d 1
   5.3G    ./data
   25G     ./tablespace
   30G     .
   [root@db1 as16]#
   
   On my Repo Server pgbackest info says ....
   
   full backup: 20251114-121504F
               timestamp start/stop: 2025-11-14 12:15:04+05:30 / 2025-11-14
   12:20:58+05:30
               wal start/stop: 000000010000000500000024 /
   000000010000000500000024
               database size: 3GB, database backup size: 3GB
               repo1: backup size: 431.0MB
   
   Could someone shed some light on    431 MB and database size:3GB, database
   backup size : 3GB  compared to the DB cluster on disk usage output ?
   
   How to correlate the pgbackrest ( info) database size, database backup size
   and repo1 backup size     and actual du output on DB cluster.
   
   Note: I am using zst compression on pgbackrest
   
   
   Regards,
   Krishane
   

2. Re: Pgbackrest info output interpretation

   Ron <ronljohnsonjr@gmail.com> — 2025-11-14T13:42:46Z

   On Fri, Nov 14, 2025 at 3:27 AM KK CHN <kkchn.in@gmail.com> wrote:
   
   > Hi,
   >
   > I am having confusion trying to understand the database size, backupsize
   > and repo backup size..
   >
   > In my DB server I have du output as follows.
   >
   > /data/edb/as16
   > [root@db1 as16]# du -h -d 1
   > 5.3G    ./data
   > 25G     ./tablespace
   > 30G     .
   > [root@db1 as16]#
   >
   > On my Repo Server pgbackest info says ....
   >
   > full backup: 20251114-121504F
   >             timestamp start/stop: 2025-11-14 12:15:04+05:30 / 2025-11-14
   > 12:20:58+05:30
   >             wal start/stop: 000000010000000500000024 /
   > 000000010000000500000024
   >             database size: 3GB, database backup size: 3GB
   >             repo1: backup size: 431.0MB
   >
   > Could someone shed some light on    431 MB and database size:3GB, database
   > backup size : 3GB  compared to the DB cluster on disk usage output ?
   >
   > How to correlate the pgbackrest ( info) database size, database backup
   > size and repo1 backup size     and actual du output on DB cluster.
   >
   
   Do you have the job log at "detail" level?  That lists every file which is
   backed up.  Sadly, no compression rates.
   
   -- 
   Death to <Redacted>, and butter sauce.
   Don't boil me, I'm still alive.
   <Redacted> lobster!
   

3. Re: Pgbackrest info output interpretation

   Greg Sabino Mullane <htamfids@gmail.com> — 2025-11-14T13:48:57Z

   The "database size" is going to be your data directory, MINUS your pg_wal
   directory, MINUS unlogged/temp relations, and MINUS things that are not
   needed for recovery (i.e. all the small pg_ directories such as
   pg_subtrans). The "database backup size" is how much of that 3GB is part of
   *this* backup - for a full backup, the number will be the same, for diff or
   incr, it will be a lot less. The "repo backup size" on the last line is the
   compressed size of the previous "database backup size"
   
   How to correlate the pgbackrest ( info) database size, database backup size
   > and repo1 backup size     and actual du output on DB cluster.
   >
   
   You cannot, really, without deep knowledge of things like which files on
   disk map back to unlogged tables. However, du on the datadir minus all pg_
   dirs should get you in the ballpark. As a quick example:
   
   cd $DATADIR
   du --summarize * | awk '!/pg_/{x=x+$1}END{print x}' | numfmt --to=iec
   
   Cheers,
   Greg
   
   --
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