With VDI extra sync 4min35s
Vanilla: 3min17s
which is consistent with 'qemu-img convert' (slightly less overhead due to some phases in installation is actually CPU bound).
Still much faster than other "sync-after-metadata" formats like VPC (vanilla VPC 7min43s)
The thing is he who needs to set up a new Linux system every day probably have pre-installed images to start with, and others just don't install an OS every day.
On Sat, May 9, 2015 at 2:39 PM Stefan Weil <
address@hidden> wrote:
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
<
address@hidden>
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
real 0m0.402s
user 0m0.206s
sys 0m0.202s
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