Re: Need to replace hdisk0 in a 2-way mirrored rootvg

You probably didn't have enough time to make a 3rd copy, but that is
what I would have done. Works fine. Only one of my AIX systems boots on
hdisk0 anymore, so I don't expect it. The hdisk numbering is going to
change around anyway all on its own. Adjusting the bootlist is something
I've gotten used to doing.

Making a third mirror, and adjusting the bootlist accordingly, would
allow you to have a normal reboot in case the IBM CE did something while
replacing that disk which caused the system to come down unexpectedly.
Something such as snag a power cord and yank it out of its socket. If
you didn't adjust the bootlist, and something happened, it probably
wouldn't come back up unless you went into microcode while it was down
and removed hdisk0 from the bootlist so it would be forced to boot
hdisk1. This is VEEERY slow, and would prolong the outage by several
tens of minutes, with your boss standing behind you nervously breathing
down your neck.

At the very least, when you break the mirror, you should change the
bootlist to contain only hdisk1, so it would not attempt to boot from
the missing, or brand-new and unformatted, hdisk0 in case of a crash.
This way, if something happened, it would come right back up on hdisk1,
quickly.

DISPLAY PRESENT BOOTLIST:

# bootlist -m normal -o

SET THE BOOTLIST TO JUST hdisk1:

# bootlist -m normal hdisk1

Roger Deschner University of Illinois at Chicago rogerd@xxxxxxx



On Fri, 3 Nov 2006, Green, Simon (EDS) wrote:

Doing it the other way and making a third copy on hdiskX would be OK but
you'd have to adjust your bootlist, and it could lead to confusion in the
future as people tend to expect rootvg to be on hdisk0. I've never actually
tried using mirrorvg to create a third copy of a VG that's already mirrored,
but I guess it'd work.

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