Avoiding the gotchas of
AIX LPAR migrations
(Level:;Intermediate)
By Christian Pruett ( pruettc@gmail.com),
Senior Systems Administrator, Freelance
First;published;by;IBM;at;IBM;developer Works;AIX;( http://www.ibm.com/developer-works/aix/).;All;rights;retained;by;IBM.
16 June 2009
Many;times;in;the;computing;world,;systems;that;worked;well;a;year;ago;outgrow;their
hardware;and;suddenly;require;more;resources.;Fortunately,;with;the;latest;AIX;LPAR
technology,;it;has;become;much;easier;to;migrate;a;server;from;one;piece;of;hardware;to
another;with;little;downtime.;The;virtualization,;portability,;and;manageability;that;IBM
pSeries®;and;System;p®;hardware;offer;provide;flexibility;in;systems;administration;and
support.;But;there;can;be;a;few;speed;bumps;along;the;way;in;the;process;of;migrating
to;an;AIX;LPAR.;This;article;focuses;on;avoiding;the;common;“gotchas” that;can;spring;up
and;slow;down;AIX;LPAR;migrations.
Frequently used acronyms – DBA:;Database;administrator,;I/O:;Input/output
Gotcha 1: Resource shortfalls
The;first;and;most;important;thing;in
moving;to;a;new;LPAR;is;to;ensure;that
sufficient;resources;are;available.;The;most
common;reason;for;moving;is;that;the
resources;on;the;original;hardware;are
no;longer;able;to;support;the;purpose;of
the;server.;Nothing;is;worse;than;putting
in;long;hours;only;to;find;that;the;new
hardware;lacks;power;and;functionality.
Gotcha 2: Establishing the
root volume group
Moving;on;to;the;technical;side;of;LPAR
migrations,;the;first;thing;you;must
manage;is;the;root;volume;group;(rootvg).
Just;as;a;house;needs;a;firm;foundation,
the;rootvg;must;be;solid;for;the;migration
to;be;successful.;There;are;three;main;ways
to;establish;the;rootvg,;each;with;its;own
pros;and;cons.
Although;the;purpose;of;this;article;is
not;to;serve;as;a;sizing;document;for
architecting;LPARs,;it;is;critical;that;the
new;LPAR;have;all;the;necessary;features.
How;many;and;what;kind;of;processors
will;you;need?;Will;the;processors;be
dedicated,;or;will;they;come;from;a;shared
pool?;Will;there;be;enough;memory?;What
about;the;I/O;adapters?;Is;it;worth;setting
up;a;virtual;I/O;(VIO);server;to;manage;the
resources?;Are;there;any;floor,;rack;space,
power,;or;cooling;restraints?
To;answer;these;and;other;questions,;IBM
provides;the;Systems;Workload;Estimator
(see;Resources).;This;tool;can;provide
approximate;sizing;information;for;the
new;equipment;you’ll;need,;as;well;as;a
general;idea;of;the;type;of;equipment
you’ll;need.;You;can;then;combine;the
information;from;the;tool;with;information
from;third-party;vendors;to;properly
determine;the;resources;needed;to;meet
LPAR;requirements.
Strategy 1: Fresh operating system
installation
Here,;the;operating;system;is;installed;from
CD,;DVD,;or;Network;Installation;Manager
(NIM);on;the;disks;to;create;the;rootvg.
Pros:;This;installation;is;the;cleanest
and;most;pristine;way;of;loading;the
operating;system.;Over;the;years,;I;have
seen;servers;that;have;migrated;through
every;version;and;release;of;AIX;from
4.3.2;to;5. 3,;and;even;though;the;AIX
operating;system;migration;process;is
one;of;the;most;robust;upgrade;paths
around,;fragments;of;software;and
third-party;applications;can;sometimes
sludge;their;way;through;the;operating
system;iterations.;These;elements;can
make;the;server;look;unsightly;at;best
or;complicated;and;difficult;to;upgrade
and;manage;at;worst.;But;by;using;base
media,;the;operating;system;is;guaran-teed;to;be;just;it;was;when;it;rolled;off
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