adconrad@shiva:/srv/test$ bunzip2 -c Packages.bz2 > Packages
adconrad@shiva:/srv/test$ xz -4 -c Packages > Packages.4.xz
adconrad@shiva:/srv/test$ xz -6 -c Packages > Packages.6.xz
adconrad@shiva:/srv/test$ cat Packages.bz2 > /dev/null && time bunzip2 -c Packages.bz2 > /dev/null && for i in Packages.4.xz Packages.6.xz; do cat $i > /dev/null && time unxz -c $i > /dev/null; done

real	0m10.046s
user	0m9.992s
sys	0m0.047s

real	0m4.015s
user	0m3.945s
sys	0m0.070s

real	0m3.858s
user	0m3.805s
sys	0m0.047s
adconrad@shiva:/srv/test$ cat Packages.bz2 > /dev/null && time bunzip2 -c Packages.bz2 > /dev/null && for i in Packages.4.xz Packages.6.xz; do cat $i > /dev/null && time unxz -c $i > /dev/null; done

real	0m10.039s
user	0m9.836s
sys	0m0.188s

real	0m4.017s
user	0m3.898s
sys	0m0.109s

real	0m3.849s
user	0m3.766s
sys	0m0.078s