The evolutionary replacement for ext3, ext4 was announced as production quality as of Linux kernel 2.6.28. A variety of fixes involving delayed allocation were applied between that and version 2.6.30, but more importantly for PostgreSQL, some bugs involving fsync handling were not fully corrected until kernel 2.6.31.8/2.6.32.1. Kernel 2.6.32 is the first version that includes an ext4 version that should be considered for a production PostgreSQL database. This is the version that both RHEL 6 and Ubuntu 10.04 are using, in the first long-term release from each that includes ext4 support.
The 16 TB filesystem limit of ext3 theoretically does not exist for ext4, but as this is being written, the associated mkfs utility is still stuck at ...
