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SubjectRe: Notebook disk spindown
Russell King wrote:
> > *a silent hard disk hard disk is no longer feasible since kernel
> > 2.2.11*.
>
> Yes it is. I have one of my machines (which NFS serves a NFS root
> client, both of which are on 24 hours a day) capable of spinning
> down for up to 4 hours at a time, with no kernel modifications
> what so ever.

You're right, but what you're missing is that with "noflushd", it was
possible to keep the disk spun down _even with pending writes_.

> It does. You really want to think about how you partition your disk
> in conjunction with what the filesystems will contain, and what options
> you want to mount with. The options that you're looking for are:
>
> nodiratime
> noatime
>
> Use of these prevents the update of the "access times" for files.
>
> Oh, I also have /var/run and /var/lock as a ramdisk (they only
> refer to current system state).
>
> Some user space programs will need to be modified - cron and ypbind
> are the two that spring to mind. cron to prevent it writing to
> /var/log/cron (not the security concerns with this mod), and to place
> ypbind's temporary file that it polls once every 10 seconds into
> /var/run.

These suggestions are good for laptops because they reduce the amount of
pending writeback, even with "noflushd".

However, they still don't save you from spinning up the disk when you
_do_ write something and you have enough RAM to hold the data for a few
hours until you must spin up the disk.

E.g. you might compile a program or send some mail. These things write
to the "disk", but you don't have to really spin up your disk if there's
enough RAM to hold the pending writes. With laptops, people are willing
to assume the RAM is reliable -- accidentally pulling the plug out won't
lose the data.

-- Jamie
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