Marek, here are my results from a simple and small read-only test. libguestfs 1.11.13 The test is to run the command below 3 times in a row for each memory setting, and take the elapsed time of only the final run. LIBGUESTFS_MEMSIZE=nnnn \ guestfish --ro -i -d F14x64 \ inspect-list-applications /dev/vg_f13x64/lv_root > /dev/null The test machine is my laptop which has 4GB of RAM and is mostly idle. 257 0m14.908s [note 1] 500 0m14.773s [note 2] 1024 0m14.886s 2048 0m14.855s 4096 0m14.861s 8192 0m14.908s [note 3] 32768 0m17.580s [note 3] Apart from the 32GB guest, those times are well within the margin of variability. Essentially they all take the same amount of time except for the last one. Rich. --- Notes: [1] Minimum permitted size. [2] Default setting. [3] I had to enable Linux memory overcommit for this test. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming blog: http://rwmj.wordpress.com Fedora now supports 80 OCaml packages (the OPEN alternative to F#) http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora