[CentOS] Adding RAM

John jses27 at gmail.com
Wed Dec 10 16:41:54 UTC 2008


On Wed, 2008-12-10 at 17:02 +0100, Peter Kjellstrom wrote:
> On Wednesday 10 December 2008, John wrote:
> > On Tue, 2008-12-09 at 12:07 -0500, Ross Walker wrote:
> > > On Dec 9, 2008, at 10:59 AM, Matt <lm7812 at gmail.com> wrote:
> > > >>>> Setting scheduler is global in C4 it can be set as a kernel option
> > > >>>> with a scheduler=deadline in grub.
> > > >>>
> > > >>> Is that an alias for "elevator=deadline" (which I know works)?
> > > >>
> > > >> No that was me forgetting the option name.
> > > >>
> > > >> Thanks Peter, it's elevator= not scheduler=
> > > >
> > > > Does this mean I need to add "elevator=deadline" to grub.conf?  Is
> > > > there a way to make the change without rebooting?
> > >
> > > I'm afraid not, so possibly a late night or weekend event with the
> > > option for a mid day reboot to recover if things turn out badly.
> > >
> > > Virtualize things and you can minimize downtime with snapshots.
> >
> > [root at blah ~]# cat /sys/block/hda/queue/scheduler
> > noop anticipatory deadline [cfq]
> > The Schedular is CFQ and can be changed on the fly to whatever Block
> > Device you want it.
> ...
> > [root at blah ~]# echo 'deadline' > /sys/block/hda/queue/scheduler
> > [root at blah ~]# cat /sys/block/hda/queue/scheduler
> > noop anticipatory [deadline] cfq  -- Changed to Deadline.
> 
> ...this is correct on CentOS-5. On CentOS-4 you need to do it via grub and a 
> reboot.

Errr,,, It can done on any 2.6 kernel system. See the Kbase Knowledge
Section at kbase.redhat.com. If he chooses to do it in grub the correct
way is elevator=deadline. I know this to be fact because I my self have
a 4.x system with high I/O with samba and use rc.local to change it upon
boot. My personal opinion of this OPs thread is that RAM is not going to
help in no way possible. What chipset, north and south bridge does the
server have? One thing I've never understood is why admins want to throw
ram at a problem that does not exist. It seems to me the solution is
always through some ram in it??? That is from experiance and my opinion.
There is more to it than just that.

JohnStanley




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