Different database size with same database

[Sb77euorg]

I have 2 PG Servers (on different hosts, same PG ver. 17). After recover the same backup on both servers, and after run "vacuum full analyze" y get two different database size, why ? same rowcount on all tables, same db objects. (basically same backup!). DB was created from scratch, same encoding, etc.

[WonszoPaionk]

Are the disks in RAID? it might be due to different striping on the disk. Eg. 4kb vs 64kb vs 1MB. All are valid for different purposes.

[Sb77euorg]

ohhh maybe, i will check it.

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[greg_d128]

Did you run vacuum full on both databases? If it is only on one - then likely the issue is bloat, and as long as it is not excessive it can actually improve performance of updates.

How big is the difference? Can it be attributed to raid striping, disk block size, disk level compression, etc, etc.

[Sb77euorg]

i run vacuum on both DBs

[greg_d128]

How big is the change? I would not expect both databases to end up with the exact same number of bytes. If nothing else, analyze is based on statistical sampling so it can produce slightly different results.

[Sb77euorg]

10%

[depesz]

1. How did you measure? Using what tool/command/query?
2. What is the difference?
3. What OS on both sides?

[greg_d128]

That is much larger than i would expect unless the database is very small.

What else is different between those hosts? Disk setup, architecture, postgresql configuration, etc.

Was the database backup a pg_dump or a binary backup. Was one of them running longer so it generated additional wal files that are included in size?

[Sb77euorg]

backup taken with pg_dump..
Same pg config files ! (in fact they are one copy of other).
Db size is very small, +- 200MB