Re: IDE freeze for seconds

Mark Lord (mlord@pobox.com)
Fri, 27 Nov 1998 15:10:15 +0000

Johnny Tevessen wrote:
>
> Hi!
>
> I've got four IDE drives (hda..hdd). They're told to go to sleep
> after a while. But when some application needs to use a file on one
> of them, both the application itself and parts of the system (other
> tasks) get frozen for some seconds if the given drive needs to spin
> up first.
>
> I think this wait period should only affect the kernel fs thread
> that tries to read from the hd, but not the applications?

That might work if the FS ran on a separate thread.
But under Linux, the "fs thread" *is* the application process.

The reason other tasks may also be held up during the spin-up
is that the disk-queue is blocked on the r/w request that
caused the spin-up, and other requests for the same MAJOR
(IDE interface) cannot proceed until it is serviced.

Other IDE interfaces are free to continue working in parallel.

-- 
mlord@pobox.com


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