[abhibeckert]

Because compression is robbing Peter to pay Paul. It saves money on storage, but costs money in compute.

And a lot of data is already compressed (images, etc) so might increase your compute cost without any storage savings.

Filesystems are often the wrong level in the stack to do compression. You want individual control over what data is compressed.

[riku_iki]

> so might increase your compute cost without any storage savings.

I agree with this point, but I think those online compression algorithms add very little overhead, so it is mostly about if Postgres adds enough other benefits compared to your current DB.

The bigger issue potentially is that ext4 is faster than zfs and btrfs itself regardless of compression.

[abhibeckert]

The compression penalty is actually massive. The bytes you're trying to read might require reading other bytes elsewhere on the disk in order to decompress them.

It's not just compute power, I was generalising with that statement. The real world speed hit can be as bad as read speeds an order of magnitude slower than if you disable compression.

You really only want to compress data where it makes sense to compress it.

[riku_iki]

> The bytes you're trying to read might require reading other bytes elsewhere on the disk in order to decompress them.

data is compressed and decompressed in blocks..