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Re: [zfs-discuss] (home NAS) zfs and spinning down of drives

Subject: Re: [zfs-discuss] (home NAS) zfs and spinning down of drives
From: Cindy Swearingen
Date: Thu, 05 Nov 2009 10:02:10 -0700
The zfs/power management CR and friends are filed. See this CR:

fs/pm - storage power management, phase I


On 11/04/09 19:02, Marion Hakanson wrote:
[email protected] said:
Thanks for the link, but the main concern in spinning down drives of a ZFS
pool  is that ZFS by default is not so idle. Every 5 to 30 seconds it closes
a transaction  group (TXG) which requires a synchronous write of metadata to

You know, it's just going to depend on your usage.  On my home machine
(Solaris-10U6 with U8-level patches), the drives are set to spin down
after 30 minutes of idle time.  I'm not certain if the root pool spins
down, but the drives in the 2nd mirrored pool do spin down.  This pool
contains my Solaris home directory and the Samba-connected datasets for
backups of other computers.

It is true that I have to make sure Thunderbird and Firefox are not
running in order to idle the home directory.  Then the drives spin down
and seem to stay that way until I wake up the display by moving the
mouse or accessing the keyboard.  They will also spin up when a nightly
backup kicks off on one of the other systems, or if I SSH-in from work
to check something.

I don't do anything special other than stopping Thunderbird and Firefox
when I leave the computer.  I just select "Lock Screen" from the Gnome
Launch menu, the screen-lock window pops up, and the display goes into
power-save mode shortly after.  I don't think there's anything magic
about ZFS with regard to keeping the drives busy.

The fancy power-saving stuff was done by Green-Bytes;  There they modified
ZFS to do the meta-data updates onto Flash-based SSD's separate from the
rest of the usual pool drives.  That way things like ZIL activity did not
have to spin up a large number of data drives just to make small metadata
updates, etc.



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