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SubjectRe: ext3: kjournald and spun-down disks
On Tue, 27 Nov 2001, Daniel Kobras wrote:

> On Fri, Nov 23, 2001 at 05:25:46PM -0800, Andrew Morton wrote:
> > Also, if we had appropriate hooks into the request layer, we could detect
> > when the disk was being spun up for a read, and opporunistically flush
> > out any pending writes.
>
> Actually you can't. SCSI spinup code isn't very useful anyway, and IDE disks
> mostly handle spinup themselves. The kernel has too issue a reset to get a
> disk back alive from sleep mode, but revival from standby doesn't involve
> the kernel at all. When using the disk's internal timer, it isn't involved in
> spindown either. Teaching the request layer about disk state might therefore
> turn out to become rather messy, I suspect.

Depends on how far you want to take it. The kernel can of course query to
discover whether a device is on standby and delay writes if possible
before actually initiating a flush.

--
"Love the dolphins," she advised him. "Write by W.A.S.T.E.."

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