In starting with the Threaded I/O Tester, the Debian Linux performance was unchanged between Squeeze and Wheezy when measuring eight threads of random writes. Debian GNU/Linux Squeeze shipped with the Linux 2.6.32 kernel while the forthcoming Wheezy is shipping with the Linux 3.2 kernel. Between Squeeze and Wheezy was also the change for the Linux version in defaulting from EXT3 to EXT4. With the unchanged performance, there's likely overhead elsewhere in the kernel bottlenecking this test. Meanwhile, for Debian GNU/kFreeBSD with the UFS file-system, it was faster for this random write test. Debian GNU/kFreeBSD Squeeze had the FreeBSD 8.1 kernel while the Wheezy release is based upon the kernel from FreeBSD 9.0.
CompileBench was much faster on Debian GNU/Linux over Debian GNU/kFreeBSD, but both versions regressed in moving from Squeeze to Wheezy.