DVD Boot time?

  • Thread starter Thread starter Davej
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Davej

I'm guessing that booting off a DVD is very slow. Are there any other
options for a read-only boot drive?

Thanks.
 
Davej said:
I'm guessing that booting off a DVD is very slow. Are there any other
options for a read-only boot drive?

Thanks.
Click to expand...

A DVD might give you 5MB/sec speeds, and 130 millisecond seek speed.
(time to move the head across the surface). As storage devices go,
that is pretty slow.

*******

In the good ole days, hard drives had a "write protect" jumper, that
would allow running them such that they wouldn't accept a write.

The function existed mainly on SCSI drives.

It appears SAS drives may have continued the tradition, as a
write protect jumper is shown here. This would be pretty fast
as a boot device. And *very* expensive to set up.

http://forums.seagate.com/t5/Savvio...6855LW-Documentation-Incorrect-File/m-p/30291

I'm not sure regular Windows would like it very much, if you installed
on a drive, shut down, then inserted the write protect jumper.
Windows might crash, if faced with a situation that the
storage subsystem reported it was read-only. It's not designed
for it, without a scheme in place to accept writes.

Some other OS setups would tolerate it. I have Knoppix loaded on a
USB2 flash stick, and the storage is separated into two areas. The
original OS image is something like a SquashFS file, and may not
be writable. There is a second storage space, called "persistent store",
and that holds any files that have been updated. If you delete the
persistent store contents between boots, that may give you roughly the
equivalent or read-only, in that you can wipe any changes made.

You can also set them up, without a persistent store. I believe there
are some USB distros, that run purely read-only and work as if they
were a CD or DVD. And if you got yourself one of the new USB3 flash
sticks, you'd be able to do better than 30MB/sec.

The topic of boot time came up the other day. There are no miracles for
boot time, because a significant chunk of the time is spent at BIOS
level. So even if the software came "flying off the disk", you'd be
looking at 40 seconds plus, as a best case. Lots of things on
computers are "hurry up and wait" situations, and the BIOS can wait
up to 35 seconds in the hope that a slow hard drive will report in.

An OS such as SplashTop/ExpressGate is probably about as close
as you'll get today, to "instant on". ExpressGate runs at the
BIOS level, and by cutting out discovery time for hard drives,
is able to start faster. They quote 5 seconds here.

http://en.wikipedia.org/wiki/Expressgate

Windows has SteadyState, which can be set up to give the appearance
of being read only. As far as I know, there is an option to
toss out all changes made since the last session. Such an option
might see use in a public library computer, or in an Internet Cafe.

http://en.wikipedia.org/wiki/SteadyState

Paul
 
I'm guessing that booting off a DVD is very slow. Are there any other
options for a read-only boot drive?

Thanks.
Click to expand...

No, it's not. The system IO files and a command interpreter load
quicker than you can count to three. After that it's as slow as
whatever is loading. Options are limitless provided there's a level
of support from the host machine's ROM/CMOS into peripheral hardware
and additional system-level drivers as needed. All certainly an other-
liness that wouldn't be seen as other than an obfuscating rat's nest
of backassed wires and kludge, FUBAR for mainstream purposes. :)
 
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