Disk mirroring 1

[sendhilk]

Hi,

I have a system with two volume groups , the rootvg and the datavg both on the internal disk. now i have connected an external disk array to this machine. i want to mirror both the root and the datavg. my question is can i mirror the rootvg on the external disk. can it be made bootable too.could anyone please brief me on how to go about this process.

Thanks,
Sendhil

 

[bjverzal]

Whether or not it is bootable can't be said based on the information you have included. What make/model is the external disk system ?

You can definitely mirror both of the VG's, as long as the unit is compatible with AIX.

Thanks, Bill.

 

[sendhilk]

Hi Bill,

Its an 7133-500 SSA Disk array.

Thanks,

Sendhil

 

[bjverzal]

The best way to tell is to create a bosboot record on one of the disks.

bosboot -ad /dev/hdisk# -U

Generally, if it creates it, it should be able to boot off it.

That is about all I can say. I remember a document in the past where IBM listed all of the know bootable external hardware units, but I don't recall the URL.

Thanks, Bill.

 

[tcorum]

If I am faced with the same problem currently and we have plans to fix it in another week when we have time to cycle the system for a moment. The solution I have came up with was to use the two internal drives to mirror the rootvg and move the datavg to an SSA disk. Given I have not actually made the move yet but I don't think it will be that difficult to move it over if you create a new vg on the SSA drive and use cplv or if you use smit then it would be smitty lv and look for the copy logical volume. If anyone else has a better plan of action, I would be more then happy to hear it.

Thanks,

Tcorum

 

[aixqueen]

I agree you can mirror rootvg internally on the two disks..then there is usually no problem with bootability. I assume you want a separate adapter for each and that is why you want the external for your mirrored device? A lot of external do not boot unless they have the right adapter....It had to do with walking the bus to find a device before the device drivers were loaded for external devices......

You could make the external a separate volume group and use the savevg to back it
up and restore it on the external. If you did have a crash, you could also move to another machine if you needed to........just a thought.

 

[thebigone]

We are booting rootvg from external SSA.
It works nicely. The only issue is that the SSA drives do not always keep the same "hdisk" number.

This is most evident when you are performing something like a migration upgrade/install. When booting from the CDROM, the names of the individual SSA drives are likely to change. The CDROM boot process numbers the disks the way it sees them, not the way the system saw them when you last built it.

Before booting on CDROM or from any other media, record the Serial number of the pdisk in addition to it's hdisk and pdisk numbers. IBM has a Service Aid under the TASKS option from a maintenance boot and diagnostics that allows you to relate the physical serial number of the SSA pdisk to a logical hdisk name.

Once you have this relationship discovered during your Maintenance IPL, you can then choose which drive(s) your rootvg resides on and procede with your upgrade.

Remember that the SSA drives are named/numbered in order of the physical serial numbers of each drive (These are visible on the drives as well). So, in the course of day to day operations, you encounter an opportunity to replace a pdisk, you introduce new serial numbers into the SSA loop. During normal boots, this is ok, as the ODM remembers the relationships of these drives to the PDISKs. I think that this is acutally based on PVIDS. I have had to learn not to depend on hdisk numbers, or PDISK numbers for that matter, and depend on PVIDS and Physical Serial Numbers.

Having this HDISK, PDISK, PVID and Phyiscal Serial Number relationship documented somewhere other than on the system can prove to be a lifesaver, or at least a system saver.

I have seen folks try to perform a migration install on their datavgs instead of rootvgs and panic when the migration install process indicated that no rootvg was found on the physical volume selected for the migration install. They even started to re-install from a mksysb,
risking all their userdata.

Again, normal day to day operations do not present this opportunity, its the booting from CDROM or tape that consistently presents this scenario.

IBM has recently announced support for rootvg IPLs from external SSA. Make sure to update your bootlist and document the PVIDS and Physical Serial numbers of the rootvg hard drives.

 

[silvaril]

kinda 'me too' commment, sorry.

Would suggest that you keep the rootvg on internal disks, as already suggested above, and if you want alternate SCSI controllers, then buy and install a seperate one for an internal disk.

Shane

 

[Guest_imported]

you may also check your jumper setting when you want to keep "hdisk#".

 

[ElgisRamon]

What version of AIX are all of you using? My AIX 4.3.3 book says AIX won't boot from external disks!

I suggest you keep [tt]rootvg[/tt] in the internal disks and mirror the volumes on these. If you have a [tt]hd5[/tt] copy on each internal disk you can simply run [tt]bosboot -a[/tt] excluding any device name and AIX will create a bootsector/bootpointer on each disk with [tt]hd5[/tt] in it.
I hope it works...
Unix was made by and for smart people.

 

[mdet]

Hi Ramon,
sorry, I know it's about eleven months after your last contribution to this thread.
I've learned the same from my courses and reading (booting is impossible from external disks), but I also remembered that with the aid of some kind of SSA-Adapters you _can_ boot from external SSA disks. I guess "thebigone"s SSA environment does include these devices.
Besides, our customers don't want to interact with the machine while booting (choosing boot device or so).
What we recently experienced at my company is booting from external SCSI-devices works if rootvg's logical volumes are mirrored. Have you ever made new experiences in that area?
Would be nice to hear from you.

Michael.

 

[Yegolev]

Boot from SSA is possible, I think you must have a later SSA adapter but I forget the various FC that will support it. I think IBM is trying to move past SSA to ESS or whatever their SAN product is. IBM Certified -- AIX 4.3 Obfuscation