[K12OSN] New Server Capacity Thoughts.

Jamie Lists jamielist at gmail.com
Sun Jun 8 08:47:59 UTC 2008

You were talking about not mirroring swap and tmp. But if you setup 2
drives in a raid 1 isn't everything mirrored automatically?

On Sat, Jun 7, 2008 at 6:24 AM, James P. Kinney III
<jkinney at localnetsolutions.com> wrote:
> 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
> users.
> 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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