Re: Poor write performance with write-intent bitmap?

[Andre Noll <maan@systemlinux.org>]

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On 13:41, John Robinson wrote:

> >Normal shutdown should put the raid in read-only mode as last step. At
> >least Debian does that. That way even a mounted raid will be clean
> >after reboot.
> 
> Yes, I would have thought it should as well. But I've just looked at 
> CentOS 5's /etc/rc.d/halt and as far as I can see it doesn't try to 
> switch md devices to read-only.

There's no need to do that in the shutdown script as the kernel will
switch all arrays to read-only mode on halt/reboot.

Moreover, as raid arrays are automatically marked clean if no writes
are pending for some small time period, a simple "sync; sleep 1"
at the end of the shutdown script is usually enough to have a clean
array during the next boot.

An alternative way to deal with this issue is to not have a root file
system at all but to mount/link each top level directory separately.
This allows to stop all md arrays cleany.

Andre
-- 
The only person who always got his work done by Friday was Robinson Crusoe

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