Re: Multiple LPARs PowerVM and internal drives -- MIDRANGE-L

Jim,

When you get to vFC on VIOS the configuration is as simple as the
ethernet/VTL, or very close. I document my installs in such a way as to be
able to re-create them with a simple script (that is also why I hate the
new HMC GUI, I had to script the whole PowerVM LPAR creation process just
to keep my devices matches between VIOSes).
Besides, if you have the rootvg living in the SAN as well you can take
snapshots of that for backup... (I've gone diskless on all the P9s I sell
lately, is not that hard to install to SAN and I haven't had a case where
having the rootvg but not the disks would help me).

Roberto

On Tue, Feb 4, 2020 at 10:30 AM Jim Oberholtzer <midrangel@xxxxxxxxxxxxxxxxx>
wrote:

Rob,

I think it’s worth pointing out that you are using two different
virtualization techniques. VIOS and IBM i hosting together, and that each
has a very different role.

IBM i is only hosing storage in this case. Much better than VIOS for
internal storage. That’s where the NWSDs come in.

VIOS, in your case is only virtualization Ethernet and tape library (in
your case a VTL).

That’s important to note since the VIOS configuration in your case is
quite simple DR can be as simple as rebuild. If someone (Like for instance
Agile’s equipment) has VIOS hosing not only Ethernet and Peripherals, but
also storage from a SAN, then the configuration is a bit more robust (read:
complex) therefore a DR plan of rebuild may not be appropriate in that
case.

Learning the AIX commands to backup and restore VIOS is a bit different
than IBM i but once you catch on, it’s not that bad. I will admit the
learning curve for IBM i folks might be a bit steeper than others because
IBM i is so dang easy.

Jim Oberholtzer
Agile Technology Architects

On Feb 4, 2020, at 6:40 AM, Rob Berendt <rob@xxxxxxxxx> wrote:

I don't know the size of your system nor your HA plans. However I will

say this...

We have a system with only 4 drives in the system unit. One pair

mirrored for one vios lpar. Another pair mirrored for the second vios lpar.

It has one lpar of IBM with 23TB of internal SSD's in expansion units.

That lpar is a hosting lpar only and hosts the disk for four other lpars of
IBM i and one of AIX. Using the hosting lpar concept allows all guests to
use all the disk 'arms' and not have to throw money at numerous disk
controllers per lpar.

Last week I had IBM connect and do a performance lpar on the main guest,

runs INFOR LX for our ERP. They pointed out a few issues but in general
there were only two, very minor, issues with disk. One was there was too
much temporary space which can impede the use of SQL plan cache. They
suggested more frequent IPLs. I plan on using the DB2 services for
analyzing temporary space instead.

The other disk issue needs a little background information for those

unfamiliar with IBM i hosting IBM i disk. On the hosting lpar you
configure one or more NWSD's (Network Storage Device) per lpar. Each NWSD
contains 1-16 network storage spaces. A network storage space is stored in
the IFS and is automatically spread across many disks. This is how each
lpar shares all the disk arms. The guest lpar they analyzed has four
NWSD's going to it. One NWSD is only for devices other than disk. The
other 3 NWSD's host 10, 11, 9 storage spaces. Using multiple NWSD's and
multiple storage spaces can be used to help performance. The guest thinks
of the storage spaces as disks and you actually go into disk stuff in SST
to add them. Thus it thinks of them as arms and adjusts performance
accordingly. The guest thinks of the NWSD's as individual disk
controllers. Sometimes you don't create multiples initially but you do it
as the system grows. Initially most of our stuff was due to growt

h. But after a few system upgrades we've gotten a better handle on it

and preplan for multiple storage spaces spread out over multiple NWSD's.
Even so, IBM has determined that one of those NWSD's (which they saw as a
disk controller) is busier than the others and would benefit from running
the TRCASPBAL and STRASPBAL TYPE(*USAGE) pair.

So, in summary, we use internal disk and host 7.8TB to the guest IBM

analyzed and it's running pretty fat, dumb and happy. Slinging a pot of
money at external SAN may not be a magic cure all for performance.

There are a lot of other arguments for using SAN outside of performance.

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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