topic The Best way to migrate the data on raw devices in Operating System - HP-UX

The Best way to migrate the data on raw devices

Enbin Hu — Thu, 19 Apr 2001 13:26:30 GMT

Hi Experts,

I need to migrate the Oracle data that is sitting on some raw logical volumes of a retiring EMC array to a new EMC array. I have both arrays connected to my server now. What will be the best way to do this ? The server is a K class, running 10.20.

Any comments will be appreiated.

- EHU

Re: The Best way to migrate the data on raw devices

A. Clay Stephenson — Thu, 19 Apr 2001 13:36:24 GMT

I would use dd with a fairly large blocksize.
To avoid double buffering specify only bs not ibs and obs.
I'm not sure whether you are using raw disks or raw logical volumes. The answer is the same but the devices will differ.
e.g. dd if=/dev/rdsk/c2t5d0 of=/dev/rdsk/c3t2d0 bs=8000k
Obviously if you are using logical volumes then
something like dd if=/dev/vg03/rlvol1 of=/dev/vg04/rlvol1 bs=8000k.
If the input and output raw devices are not the same size you should also add the 'count=' argument to dd.

Re: The Best way to migrate the data on raw devices

MARTINACHE — Thu, 19 Apr 2001 13:45:33 GMT

Hi,

I don't work on XP but I see 2 ways :

1)
Extend your VGs with your new disks
Mirror logical volumes to the new disks
Unmirror form old disks
Reduce the vg
That's all (supposing that you have mirror disk UX, you can pvmove if not), You don't need to stop database.

2)
Create new lvols on new disks
stop database
dd if=/dev/vgXX/rOLDLVOL... of=/dev/vgXX/rNEWLVOL bs=...
start database (mount)
modify database architecture
open database.

If you use rawdevices in oder to increase performances, don't forget that you can obtain approximatively the same perf :
If you have Online-JFS, you are able to mount a filesystem with "mincache=direct" option. Then you will not use LVM.

Regards,

Patrice.

Re: The Best way to migrate the data on raw devices

Dave Wherry — Thu, 19 Apr 2001 13:56:47 GMT

I would go with the mirroring option if you have the HP mirroring software. It can all be done on-line, no down time required.

You could also try to use Oracle's mirroring functionality. I'm not sure how to use it, but I know it is there as our DBA has used it. Again, I think it can work on-line.

The dd option will certainly work. You will just need downtime as your data can not change during the process.

Re: The Best way to migrate the data on raw devices

Dave Wherry — Thu, 19 Apr 2001 14:00:59 GMT

I forgot another option, you could have EMC do it with SRDF. I'm surprised they have not already approached you about doing it.
They temporarily install SRDF on both frames and copy the data over. Then remove the old frame.
I know they do this type of consulting quite often. Of course it will not be free. Nothing from EMC is free.

Re: The Best way to migrate the data on raw devices

Enbin Hu — Thu, 19 Apr 2001 14:14:56 GMT

AC Stepheson, Patrice, Dave:

Thanks a lot for your suggestions. My original plan was to use dd, but now I think I would use the mirroring to do this instead, since the copying process can be done in the background and doesn't require the down time.

Thanks again.

EHU