On Wed, Oct 27, 2010 at 12:58:45PM +0200, Michael Monnerie wrote:
> On Mittwoch, 27. Oktober 2010 Dave Chinner wrote:
> > I'd suggest that people learn how to tweak udev hotplug rules so
> > that when the device is first created (i.e. during hotplug) the
> > scheduler, queue depth and readahead are set automatically. That way
> > you don't have to rely on devices being discovered before your script
> > runs...
> >
> > Another benefit of doing it this way is that it is easy to set
> > default rules for different types of devices based on regex matching
> > e.g. different configs for "sd*" vs "dm*" vs "vd*" are trivial to
> > set up.
>
> Sounds very nice. But the script I use will still work when upgrading
> the server from openSUSE 11.2 to 11.3, and is therefore the preferred
> choice for me.
>
> Also, I'd need to find information and learn how to tweak udev hotplug
> rules.
GIYF.
> I want to implement this on about 30 VMs on 2 different hosts,
> with 3 different release states of servers (openSUSE 11.1, 11.2 and
> 11.3).
The udev rule format hasn't changed in a long while. The same rule
set should work on all of these.
> The chance is high that I'd need two or three different udev
> tweaks for the different releases, so I don't see the benefit of udev
> for me. I wrote the script in about the same time I wrote this mail.
You'd need one regex per device type you want to tweak with
different values.
> That's always the problem between developers ("ah, cool new stuff") and
> admins ("i need this on 500 servers with least possible work for me, and
> it must still work after any updates/upgrades").
This is not "cool new stuff" - I've seen it used for exactly this
purpose for _several years_ by distros. e.g. pulling the identifier
string from the device to set hardware device specific tunables,
changing default dm/md readahead, etc. It's not new, and is easy to
configure generically so it works on a wide array of different machines.
And if you hotplug devices, it just works automatically - you don't
need to rerun a script after every hotplug...
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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