Boot LUN Migraton from one SAN to another

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KiKNAtion
Posts: 3
Joined: 2015/08/19 13:42:43

Boot LUN Migraton from one SAN to another

Post by KiKNAtion » 2015/11/11 12:55:27

Hello there,
Can someone tell me how to migrate the boot LUN from one SAN device to another ? Is there a way to get the data replication done from the OS side ? The Partitions are configured via LVM except the /boot, which is direct.
OS used: RHEL 5.9

Thanks,
KiK

aks
Posts: 3073
Joined: 2014/09/20 11:22:14

Re: Boot LUN Migraton from one SAN to another

Post by aks » 2015/11/12 18:01:09

What a complex question.
That depends on the SAN and what the SAN does with blocks and so on.
From an OS perspective (assuming MBR boot here), dd'ing the boot partition to a file and restoring it, then adding the 512 byte boot block should work, or use something like Clonezilla.

KiKNAtion
Posts: 3
Joined: 2015/08/19 13:42:43

Re: Boot LUN Migraton from one SAN to another

Post by KiKNAtion » 2015/11/30 12:01:24

@aks Thanks for the reply, I have the idea of moving data using dd through rescue mode, however
we are using SAN with multipathing, any idea how to migrate the Linux SAN boot LUN with multipathing to another SAN can be achieved?
Red Hat has confirmed no official support for this action, so no procedure from their side, however is there any way this can be done ? :?:

aks
Posts: 3073
Joined: 2014/09/20 11:22:14

Re: Boot LUN Migraton from one SAN to another

Post by aks » 2015/11/30 17:32:41

Hmmm, I guess (note this is a real guess):
1) Present the existsing and the new LUN to the machine.
2) Copy the data across (not forgetting to copy exteneded attributes across - SELinux for example - and preserve permissions).
3) Modify the mutli-pathing and fstab (UUID etc. will be different now) on the new LUN.
4) Re-install boot loader (grub) on the new LUN.
5) Un-present the old LUN from the machine.
6) Tell your boot BIOS (usually some firmware on the card) to try to boot off the new one.
7) Expect a shed load of problems I've not though of ("get out of jail card").
8) Pray and pray again.
9) With failure, un-present new, present old, adjust boot instructions and you should be back to the beginning.

But a lot of this really depends on what the SAN really does with blocks (which is why I thought if you copy from one to the other, you may mitigate SAN effects as they are "in play" when copying), which is probably why RH say don't do it!
Without the exact kit and experimentation, I could not hope to give you anything approaching accurate instructions.
Sorry.

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