My (slg_at_sci.org) original question was:
In Digital Unix 4.0 there is an option to spin down the disks after
a specified period of inactivity. Is there any way to spin down the
disk having the root file system?
The replies are summarized as follows: Most, but not all, respondents
agreed that it is possible to spin down
the root disk but in practice it will not work because frequent
requests are made by the operating system to the root disk.
Several people asked how to access the spin down feature of
Digital Unix 4.0. Try "man dxpower".
Also note from Tom Blinn's message below that a kernel parameter,
PWRMGR_ENABLED, must be turned on.
Tom Blinn wrote:
The option you cite is only available on systems that support power
management (the PWRMGR_ENABLED option turned on in the kernel config
file). Not every system does this. In fact, MOST systems do not have
power management enabled by default.
If the root disk (the one with the root file system) were ever idle
for the specified period, it would get spun down. However, there are
tasks
that touch files on the root disk periodically that generally prevent
ever
having the disk stay idle long enough to spin down. So, from a
practical
perspective, the answer to your question is "no".
Olle Eriksson wrote:
No, you can't. Also it is my experience that if you have secondary swap
on a second disk, you should disable disk spin down completely. The
pager/swapper doesn't seem to know how to spin up a disk.
Albert De Knuydt wrote:
You can (almost) always give a 'stop' command to the disk with the SCU
utility. Like this:
# coulomb> scu
scu> set nexus bus 1 target 1 lun 1 #whatever numbers apply at your site
scu> stop #spin down the thing
scu> exit
# coulomb>
I have never dared to do this on the root file system, so I have no clue
as
to how the system will behave. (Ultrix within a couple of seconds if you
do this).
Alan Rollow wrote:
Once upon a time, there was a rash of complaints from people
that didn't want their disks to spin down, because there
were. Therefore, it must be possible. Whether they'll
spin back up when needed could be the problem the others
were having. Look at dxpower.
Both AdvFS and UFS are affected by the periodic running
of sync(2) from update. If any file system on a disk has
dirty data, the disk won't stay quiet for more than about
30 seconds. Since spin-down/spin-up cycle is a significant
fraction of this, it won't be worthwhile in most cases.
Received on Wed Mar 25 1998 - 03:21:36 NZST