# [OmniOS-discuss] [discuss] illumos power management

Rafael Vanoni rafael.vanoni at pluribusnetworks.com
Wed Nov 13 17:10:53 UTC 2013

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    > On Nov 12, 2013, at 5:52 PM, "Paul B. Henson" <henson at acm.org> wrote:
    >
    >> I think the storage server I'm working on at home (current omnios stable) is
    >> spinning down disks; whenever I get back to it after not touching it for a
    >> while, anything touching my export pool (dual 6 x 3TB WD Red RAIDZ2) takes a
    >> long time to respond, and then goes back to normal.
    >>
    >> My current power.conf is:
    >>
    >> -----
    >> autopm                  enable
    >> autoS3                  disable
    >>
    >> cpupm                   enable
    >> cpu_deep_idle           enable
    >> cpu-threshold           1s
    >> -----
    >>
    >> I had thought that when running on server class hardware the default was not
    >> to spin down drives, but perhaps I was mistaken? Hmm, or maybe the default
    >> is to just skip power management completely, and explicitly turning it on
    >> turned on everything.

    At least for CPU power management, the default is to have it on.

    >> I'm thinking about adding "system-threshold always-on" to the configuration,
    >> which I guess will disable all power down functionality, other than CPU,
    >> which is controlled by the "cpu-threshold" parameter? What other power
    >> savings would this turnoff? I am in general in favor of saving energy :),
    >> other than for the disks, as the latency is too high and causes too much of
    >> a delay, and it's not clear if setting the system-threshold to stop spinning
    >> down disks will also disable other potentially desirable power savings. I
    >> guess the other option would be to explicitly configure device-thresholds
    >> for all of the disks individually. Is there any way to list what components
    >> of a system support power management?

    Yes, If you don't specify individual settings for devices,
    "system-threshold always-on" will leave everything at full power.

    I don't know of a specific way of querying PM capabilities for
    devices, but have a look at the man page for power.conf(4). It
    mentions a way of specifying policies based on generic capabilities
    that can apply to any device that supports it, instead of having to do
    it one by one.

    >> While on the subject, any thoughts on event-mode vs poll-mode for cpupm?
    >> It's not clear from the man page what the default is if you just set it to
    >> "enable".

    If the system supports it (essentially if we're able to create CPU
    power domains with information from ACPI tables), event mode is the
    default. Otherwise we fall back to polling.

    Hth

    Rafael

    >> Thanks.
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