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Re: [K12OSN] New Server Capacity Thoughts.



On Sun, 2008-06-08 at 01:47 -0700, Jamie Lists wrote:
> You were talking about not mirroring swap and tmp. But if you setup 2
> drives in a raid 1 isn't everything mirrored automatically?

Only if you set it up that way. I don't use hardware raid because I
can't control how the drives will be put to use. Hardware raid will use
the entire drive. I will typically create multiple partitions and join
them as needed to make raid components and/or LVM components.
Example:
2 250GB drives
each drive is split the same way:
100M, 1GB, 5GB, 10 GB, 50GB, 100GB, rest

The 100M are raid1 /boot, 1GB are independent swap, 5GB is raid 0 /tmp,
10GB is raid1 /, 50GB is raid1 /var, 100GB is raid1 /usr, rest is
raid1 /home

This gives me a backup boot partition (I set drive 1 as primary boot and
drive as secondary), 2 GB swap (for a 1GB RAM machine, adjust up to
total 4GB swap), 10GB /tmp that is very fast read and write, 10GB very
fast read /, 50GB secure logs and email and other stuff I don't want to
loose, 100GB fast read never write /usr application space, and loads of
secure data space for users.

Complicated? Yes. But I get to set it up to suit the needs of the
system. I can clone the box by powering off, replacing drive 2 with a
new blank drive, booting into runlevel 1, partitioning new drive 2 the
same as the old, rebooting and letting the raid sync it all up. (Yes, I
can also clone it with dd but that assumes identical drives. With the
raid method I can have a new drive that is 300 GB because the 250's were
sold out).
Yes. I am a control freak :-)

> 
> On Sat, Jun 7, 2008 at 6:24 AM, James P. Kinney III
> <jkinney 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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> >>
> > --
> > James P. Kinney III
> > CEO & Director of Engineering
> > Local Net Solutions,LLC
> > http://www.localnetsolutions.com
> >
> > GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
> > <jkinney localnetsolutions com>
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-- 
James P. Kinney III          
CEO & Director of Engineering 
Local Net Solutions,LLC                           
http://www.localnetsolutions.com

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney localnetsolutions com>
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7


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