Re: Restoring mksysb on bigger disk

From: Dale Talcott (aeh_at_cloud.cc.purdue.edu)
Date: 11/07/03 

Date: 6 Nov 03 20:43:06 EST

ketsak <member44158@dbforums.com> writes:

>No responses ????!!!!!! Need some expert advice..........

Okay, I'll speak first. Don't do it. The odds of getting it right are
too small.

>> I have RS/6K running 4.2.1 with mirrored ROOTVG on 4.3 GB disks
>> (hdisk0 & hdisk1). I want to take a system backup and JUST FOR
>> verification purpose wants to restore it on the SAME system (as I
>> don't have any spare system), but on DIFFERENT spare hard disks, of
>> the size 18 GB each. While restoring I may not be able to power
>> down/disable hdisk0 & hdisk1, i.e these two disks would be on line
>> with 18GB disks.

>> I know that before running mksysb I need to edit /image.data file to
>> change PP size to 32 MB (currently it is 8 MB for 4.3 GB disks) under
>> vg_data stanza. Also I need to verify PROMPT=YES in /bosinst.data
>> file. Now my questions are :

>> 1) Do I need to change PP size to 32 MB under all 'lv_data' stanza in
>> /image.data ?

If you have just file systems, not raw LVs, I *think* you can leave
the PP stuff alone and just set SHRINK=yes. I'm pretty sure I've done
this at least once with no problems (but this might have been on AIX
later than 4.2.1).

If 4.2.1 doesn't support the SHRINK option, then you should adjust
all PP/LP sizes and counts. At least, I have done this and had the
restore work.

>> 2) According to new PP size do I need to change FS_SIZE under
>> 'fs_data' stanza in /image.data ?

The FS_SIZE is in blocks and doesn't need to change. You might end up
with unused space at the end of the LVs, but that is not important.

>> 4) After selecting target disks under Installation & Maintenance menu,
>> still is there any possibility that restore process may affect
>> existing rootvg on hdisk0 & hdisk1 ?

Yes! That's why I wouldn't try this without disconnecting hdisk0 and 1.
Especially with such an old AIX. If I remember correctly, if you had
two sets of disks that internally claimed to have the same LVs and you
somehow activated them both at the same time, the ODM got very confused.

>> 5) To avoid probable problem mentioned in Q-4, do I need to edit
>> /bosinst.data file to reflect location of the target disks (18 GB
>> disks) under 'target_disk_data' stanza ?

I would. Just in case.

>> 6) Suppose I succeed in restoring mksysb tape on new hard disks, now
>> on simply physically removing those disks, will I be able to boot
>> from hdisk0 again without any problem ?

Depends on how you've set your bootlist. If you set it to try the new
disks first, then hdisk0, you should be okay. After you are done with
the testing, change the bootlist to hdisk0 and 1 only again.

>> 6) Do you see any other potential problem in restoring this way ? Or
>> please let me know if I may be missing some steps for successful
>> restoration on bigger disks.

Create two mksysb images, one normal and one with your edited image.data and
bosinst.data files. That way, if the second one proves unreadable part way
through, and hdisk0 gets clobbered in spite of your care, you'll still
have the first tape to recover with. 

-- 
Dale Talcott, IT Research Computing Services, Purdue University
aeh@quest.cc.purdue.edu         http://quest.cc.purdue.edu/~aeh/

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