Le 06/11/2015 18:28, Simon Hobson a écrit :
> I've done no measurements, but my "gut feeling" is that for the servers I manage (and my OS X laptop), the limiting factor is disk I/O. Thus parallelising service startup won't help much (if at all) because it just means all the services fire up and take longer each to start. Eg, (as a simplification) if you have 10 services that take 10s each to start, then they'll take 100s total - starting them in parallel probably means they'll all take 100s (give or take). All assuming no dependencies of course !

     I am booting my servers, say, once per year,  but my laptop at 
least twice per day. Booting a server takes long, for the reason Rainer 
says; I don't care much except when there's an issue I need to debug. 
For the laptop I definitely prefer to shut it down before I put it into 
my bag to take the metro.

     On the servers I have more or less big RAIDs made of 
electro-mechanical disks; on my laptop an SSD. Disk access contention 
cannot be the same for SSD and electro-mechanical disks, specially when 
you only read.

     And there is yet other categories of Linux devices: the embedded 
and hand-held...

Le 06/11/2015 19:37, KatolaZ a écrit :
> Please do not tell the systemd guys that the bios PXE boot takes so
> much time to do its work, otherwise they will go head down to replace
> it with their own parallel-faster-more-reliable-memory-eating
> systemd-PXEbootd.....

     Maybe the ultimate reason for Systemd is it was a condition posed 
by M$ to provide RedHat on Azure. In which case we talk of virtual 
machines, and I expect they don't emulate PXE boot :-)

     Didier