Re: Why host? Was: IBM i vs VIOS for Host Partition

Jim,

Thanks. I thought the arms would be a better payback than the additional
controllers.

And, I meant the second paragraph to be totally independent of the first,
like the first never happened.
<snip>
I consider this a good enough reason to host. Are there others? Well,
perhaps VIOS san support?
</snip>
Meaning basically that if you want all disk on SAN isn't hosting required?
Also asking for other reasons to host vs dedicated.

Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: Jim Oberholtzer <midrangel@xxxxxxxxxxxxxxxxx>
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>,
Date: 04/18/2013 07:34 AM
Subject: Re: Why host? Was: IBM i vs VIOS for Host Partition
Sent by: midrange-l-bounces@xxxxxxxxxxxx



Rob,

The additional power of another disk controller will not mitigate the
queuing that goes on inside IBM i for I/O, therefore unless you have six
arms or more, you are reducing the available performance of I/O.
(which might be OK in some situations where I/O is not a significant
factor in the application, but it will affect backup/restore) What
you'll have is a disk controller that's way under utilized. Put another
way, you'll only be getting about 2% or 3% of your investment in the
card back.

In the case you cite, your better off creating a series of smaller
virtual disk units so you wind up with as many as you can for the space
you need.

VIO Server really does not change the equation at all, it's just another
method of virtualization.

Jim Oberholtzer
Chief Technical Architect
Agile Technology Architects


On 4/18/2013 6:17 AM, rob@xxxxxxxxx wrote:

We host some guest partitions because it reduces the cost of hardware.

You

don't have to have a separate disk controller for each lpar. Part of me
has to wonder if 12 disk arms shared between the host and two guests

would

be a better performer then 3 dedicated lpars with only 4 arms each. Ok,

a

separate disk controller for each could blow that away though.

I consider this a good enough reason to host. Are there others? Well,
perhaps VIOS san support?

Let's take it to the extreme. Now we have a very large guest, over a
couple of TB. We did it this way because we wanted to do it "now" and
couldn't add another disk controller. The boss is saying when we get

our

new hardware (which I think will be postponed quite some time due to the
business numbers I saw yesterday), that we will make that a dedicated
lpar.


Rob Berendt
-- IBM Certified System Administrator - IBM i 6.1 Group Dekko Dept
1600 Mail to: 2505 Dekko Drive Garrett, IN 46738 Ship to: Dock 108
6928N 400E Kendallville, IN 46755 http://www.dekko.com
--

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