We have a postgres server with 6 SSDs in a raid10. backing up the postgres database with pg_dump works fine and causes almost 0 load to the disks or cpu. Tar'ing said pg_dump without any options other than -vcf seems to cause so much disk IO that queries start to timeout for a brief moment (5 minutes)
I'm trying to troubleshoot why this would be as pg_dump doesn't do this and tar should be similar to cat'ing the files together. Does writing to a luks encrypted disk require additional entropy? I thought it was entirely the key/passphrase?