Common Connect - August 2009

the;factory;floor.

Cons:;Unfortunately,;with;a;completely clean;installation,;making;the;new;LPAR look;like;the;old;server;can;be;time-consuming.;You’ll;have;to;re-create user;IDs,;groups,;file;systems,;environ-ment;variables,;and;all;the;features;that define;the;server.;If;the;server;is;simple, this;may;be;the;way;to;go.;But;if;the server;has;a;complicated;environment with;hundreds;of;users,;it;may;be;more worthwhile;to;choose;another;route.

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Strategy 2: Physical disk move

Here,;you;remove;the;physical;disks;from the;original;server,;insert;them;into;the new;hardware,;and;assign;them;to;the LPAR.

Pros:;By;taking;the;root;disks;out;of;the old;server;and;putting;them;in;the;new, you;guarantee;that;the;new;server;has the;same;identity;as;the;old;server.;Just about;everything;in;the;rootvg;will;be preserved,;and;you;can;count;on;every-thing;being;available;upon;first;boot.

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Cons:;There;are;four;reasons;why;this strategy;is;not;the;wisest;option.;First, there;is;a;chance;that;you;could;drop or;damage;the;disks;while;physically transporting;them.;Second,;the;original server;may;not;have;all;the;device drivers;to;make;the;new;hardware functional,;which;will;then;require hunting;down;and;installing;additional software.;Third,;you;will;most;likely have;to;delete;or;reconfigure;devices;to make;the;new;LPAR;functional;(I;cover this;in;more;detail;later).;Finally,;there is;a;chance;that;the;form;factor;of;the disks;will;be;incompatible;with;the;new hardware,;completely;ruling;out;this option;altogether.

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Strategy 3: System backup and restore

Here,;you;back;up;the;original;server;to;an mksysb;image,;then;lay;it;down;onto;the new;hardware.

Pros:;I;prefer;this;strategy,;because;it preserves;the;original;hardware,;allows the;new;LPAR;to;get;device;drivers automatically;(when;using;complemen-tary;base;media;or;a;NIM;server),;and brings;over;all;of;the;user;IDs,;groups, rootvg;file;systems,;and;environment variables.;It;is;the;least;intrusive;of;all the;options;for;both;the;original;server and;the;new;LPAR.

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Cons: ;The;main;deterrent;to;this;solu-tion;is;if;the;rootvg;on;the;original server;is;constantly;being;modified. The;mksysb;image;will;only;be;“fresh” for;so;long;before;the;changes;to;the original;server;cause;a;huge;delta;in;the content.;But;if;best;practices;have;been followed;in;preventing;regularly;chang-ing;data;from;being;inside;the;root volume;group,;this;option;can;provide ample;time;for;testing;and;deployment. And;you;will;need;to;acquire;temporary IP;addresses;or;network;adapters;to make;the;build;happen,;then;correct them;later.

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Also,;it;is;important;to;determine;the type;of;disks;to;be;used;for;the;rootvg disks.;Will;the;server;use;internal;SCSI disks;or;Storage;Area;Network;(SAN) boot;technology?;If;SCSI;disks;will;be employed,;patching;SAN;drivers;is;an easier;task,;but;there;can;be;a;higher likelihood;of;hardware;failures.;If;SAN boot;technology;is;used,;reboots;and;I/O performance;will;be;very;fast,;but;the disks;cannot;be;ported;from;one;LPAR;to another;easily;because;of;how;the;Fibre Channel;adapter;worldwide;name;(WWN) is;integrated;into;the;disk;attributes.

Gotcha 3: Managing external
volume groups

When;you;have;chosen;the;operating system;strategy,;it;is;time;to;plan;how;to bring;over;the;external/non-root;volume groups.;As;with;the;rootvg,;there;are several;ways;to;migrate;data;onto;the;new LPAR,;including;performing;a;backup;and restore;operation,;using;SAN;technology such;as;the;Flash;Copy;feature;on;IBM;SAN Volume;Controllers;(SVC);or;just;using;the original;cables,;adapters,;and;disks;in;the new;hardware.;But;whatever;technique you;leverage,;there;are;a;few;things;to consider.

First,;save;a;copy;or;back;up;the;/etc/ filesystems;file;from;the;original;server. Although;commands;like;importvg will;detect;the;contents;of;the;external volume;groups,;the;contents;may;not;be imported;in;an;organized;fashion,;causing file;systems;to;be;mounted;in;an;incorrect order.;I;have;seen;this;typically;when;a customer;has;several;external;volume groups;and;file;systems;are;hierarchically linked.

For;example,;consider;an;Oracle;database server;with;three;volume;groups;and interrelated;file;systems:

datavg1:;/opt/app •

datavg3:;/opt/app/oracle •

datavg2:;/opt/app/oracle/product •

If;these;volume;groups;were;imported numerically,;the;system;would;try mounting;/opt/app/oracle/product,;then over-mount;it;with;/opt/app/oracle.;But by;having;a;copy;of;the;original;/etc/ filesystems;file,;you;provide;a;reference;for organizing;the;same;file;on;the;new;LPAR.

Second,;save;a;copy;of;disk;information, especially;if;the;disks;will;be;moved directly;from;the;original;server;to;the new;LPAR.;Make;sure;to;document Physical;Volume;Identification;(PVID) numbers,;volume;group;names,;health check;intervals,;and;any;other;tunables. This;way,;disks;can;be;identified, configured,;and;imported;with;no guesswork.

Third,;consider;other;disk;maintenance that;you;can;perform;during;the migration.;Take;advantage;of;the;server being;unavailable;to;change;the;disk architecture.;You;can;change;external volume;groups;to;big;or;scalable;volume groups.;You;can;replace;numerous;small disks;with;a;single;large;logical;unit number;(LUN).;You;can;reclaim;unwanted file;systems;or;disk;space;to;save resources.

Gotcha 4: Setting up and
configuring devices

The;last;challenges;to;completing;the LPAR;migration;are;to;get;all;the;other devices;set;up;properly.;Depending;on;the strategies;you;used;earlier,;management of;the;devices;can;be;a;time-consuming task;or;an;easy;endeavor.

Before;moving;over;to;the;new;server, take;the;time;to;get;all;the;configuration parameters;from;the;existing;devices. The;lsdev –C;command;will;show;all;the devices;that;are;on;the;old;server;;you;can then;run;the;lsattr;and lscfg;commands against;that;output;to;get;all;the customized;settings;and;attributes.;Some of;these;parameters;will;not;necessarily apply;equally;to;the;new;LPAR;because;of the;different;hardware,;but;some;settings should;be;carried;over,;like;IP;aliases, memory;tunables,;and;Fibre;Channel speeds.