Am 09.05.2015 um 05:59 schrieb phoeagon:
BTW, how do you usually measure the time to install a Linux distro
within? Most distros ISOs do NOT have unattended installation ISOs in
place. (True I can bake my own ISOs for this...) But do you have any
ISOs made ready for this purpose?
On Sat, May 9, 2015 at 11:54 AM phoeagon <phoea...@gmail.com
<mailto:phoea...@gmail.com>> wrote:
Thanks. Dbench does not logically allocate new disk space all the
time, because it's a FS level benchmark that creates file and
deletes them. Therefore it also depends on the guest FS, say, a
btrfs guest FS allocates about 1.8x space of that from EXT4, due
to its COW nature. It does cause the FS to allocate some space
during about 1/3 of the test duration I think. But this does not
mitigate it too much because a FS often writes in a stride rather
than consecutively, which causes write amplification at allocation
times.
So I tested it with qemu-img convert from a 400M raw file:
zheq-PC sdb # time ~/qemu-sync-test/bin/qemu-img convert -f raw -t
unsafe -O vdi /run/shm/rand 1.vdi
real0m0.402s
user0m0.206s
sys0m0.202s
zheq-PC sdb # time ~/qemu-sync-test/bin/qemu-img convert -f raw -t
writeback -O vdi /run/shm/rand 1.vdi
I assume that the target file /run/shm/rand 1.vdi is not on a physical disk.
Then flushing data will be fast. For real hard disks (not SSDs) the
situation is
different: the r/w heads of the hard disk have to move between data location
and the beginning of the written file where the metadata is written, so
I expect a larger effect there.
For measuring installation time of an OS, I'd take a reproducible
installation
source (hard disk or DVD, no network connection) and take the time for
those parts of the installation where many packets are installed without
any user interaction. For Linux you won't need a stop watch, because the
packet directories in /usr/share/doc have nice timestamps.
Stefan
