[K12OSN] New Server Capacity Thoughts.

James P. Kinney III jkinney at localnetsolutions.com
Sat Jun 7 13:24:33 UTC 2008

On Sat, 2008-06-07 at 08:52 -0400, Rob Owens wrote:
> On Fri, Jun 06, 2008 at 11:36:27PM -0400, James P. Kinney III wrote:
> > Double the RAM. Flash does NOT thread or share a library. Each flash
> > applet on a page opens a full instance of flash. Yuck!
> > 
> > If possible, put a second drive as a mirror in each server (and use
> > noatime in the /etc/fstab!). This will have a dramatic impact on
> > application performance. 
> I've been doing this, but I've also been wondering if there are any
> reasons not to do it.  I've read the kernel mailing list thread about
> it, and there are mentions of "a handful of applications" that don't
> behave properly with noatime specified.  Do you know anything about
> that?

To my understanding, atime may impact selinux and few other security
applications. These are things will impact only the admin and not the

As for reasons to not use a second drive as a mirror: cost
> >Be sure to NOT have /tmp in the mirror (it can
> > be a raid0 striped array).
> >
> Could you explain why not to mirror /tmp?  I'm interested.  

The data in /tmp is temporary and often contains just a marker that
something exists or a pipe. By putting /tmp on a mirror, every write
must be done to each drive. As data redundancy is not important for /tmp
data this will only slow down the machine.
> And while I'm asking, what are your opinions on mirroring swap?

Don't. Swap already has the ability to handle itself very well. What
does work well is to create 2 swap partitions the same size on different
drives. swap will write part to one and the rest to the other. It works
in chunks that don't equate to files but to memory pieces.
> -Rob
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James P. Kinney III          
CEO & Director of Engineering 
Local Net Solutions,LLC                           

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney at localnetsolutions.com>
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