Mirroring rootvg

[pvachon]

I’m using AIX 4.3.3. I’d like to mirror the rootvg but instead of keeping the copy always up to date (like normal mirroring process), I would like to update the copy ONLY when I want to (every night for example). This would allow me to keep maximum performances for the users during day and the ability to boot from another disk in case of a hard disk failure. So the system would turn normally while I’m getting a replacement drive. I think this would be a great compromise between availability and performances. Is there a way to do this?

Thanks

 

[bi]

Depending on what kind of hardware you have and which filesystems you have put in rootvg (for example, have you put user or application filesystems in rootvg?), mirroring rootvg really shouldn't give you a huge performance hit. If you have put user and application filesystems in rootvg, or if your users write a lot to their home directories, then you may get a performance hit. (And if your users do write a lot to their home directories, you might want to consider moving /home to another vg, although purists definitely frown on this.)

I'm not even sure if you can do it. One alternative would be to create a mksysb tape every night (which would sort of accomplish what you want). However, booting with a mksysb tape and recovering all of rootvg with it took me a minimum of two hours to complete.

good luck.

 

[pvachon]

The /home is not in the rootvg.

I found I way to do this, but I'm not sure if it's OK.
After mirroring the rootvg, you can use the command chlvcopy -b -l <lvname> to temporarily stop the mirroring. The -l <lvname> option is used to create a /dev special file that points to the copy of the lv. So you can perform a full backup of this lv without worrying about file change. This option a another advantage : the lv is not automatically 'resync' at boot time. To remerge the mirrors, you must run chlvcopy -B and syncvg to update them (see AIX Logical Volume Manager From A to Z : Introduction and Concepts, page 270,

http://www.redbooks.ibm.com/redbooks/SG245432.html).

That's exactly what I'm looking for, but I wonder if I would be able to boot from the mirror in case of a drive failure.

 

[pvachon]

Maybe it could work. The chlvcopy man page says :

&quot;If the persistence flag (-P) is set [the -l flag also sets the persistence option], the following applies: In the event of a crash while an online backup copy exists (or multiples exist), the existence of copies is retained when the system is rebooted.&quot;

 

[pvachon]

I got it! Mirroring is not the way to do this. The good way is Alternate Disk rootvg Cloning.

&quot;Cloning the rootvg to an alternate disk can have many advantages.
[ul][li]Having an online backup available in case of disaster. Keeping an on-line backup requires that an extra disk or disks to be available on the system.[/li]
[li]Applying new maintenance levels or updates. A copy of the rootvg is made to an alternate disk, then updates are applied to that copy. Finally, the boot list is updated to boot from the new device. The system runs uninterrupted
during this time. When it is rebooted, the system will boot from the newly updated rootvg for testing. If updates cause problems, the old rootvg can be retrieved by resetting the bootlist and rebooting.&quot;[/li][/ul]

The complete procedure can be found in the IBM Certification Guide AIX V4.3 System Administration redbook (SG24-5129-00).

 

[ElgisRamon]

Remember you must to reconstruct your BLVs (with [tt]bosboot -a[/tt]), update your bootlist with [tt]bootlist -m normal hdiska hdiskb!


I hope it works...
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