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Re: Does Creating an Array Erase Disks???

 
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kris rombauts
Honored Contributor
Solution

Re: Does Creating an Array Erase Disks???

Dan,

did a quick test for you on Windows 2003:

- created raid0 array with one logical drive on one physicall disk
- formatted NTFS, copied 6 GByte files on it
- removed disk from server
- hot inserted it in another running server
- started ACU utility/rescanned bus
- saw one unconfigured disk
- created raid0 array with one logical drive on this disk
- started disk manager and saw this disk as "Healthy" but no drive letter.
- assigned drive letter
- all data was visible and chkdsk ran without any error, could copy new files to
driveletter, all looks ok.

....

I don't consider this as a supported method but at least on Windows it seems to work just fine without downtime.


HTH

Kris
kris rombauts
Honored Contributor

Re: Does Creating an Array Erase Disks???

..... so the point is that if you create the array with the same properties (stripe size ,logical drive size ..etc) the data does not get erased by just creating the array and logical drive information again as it writes just that piece of configuration information onto the disk(s).


Kris
Dan Hawker
Advisor

Re: Does Creating an Array Erase Disks???

Hi Kris,

Thanks for trying that for me. That is certainly promising and more as I'd expect. I was just unsure as to whether the array/logical volume creation was would be more destructive of the disk than that.

As you say, no guarantees, but certainly more hopeful...

I'd guess that the controller sets aside a small area of the disk for the controller info and this is the area that gets edited/wiped when moving drives around from machine to machine.

I've managed to organise a reboot of this machine in a couple of days, so I'll probably leave it until then and give it the kick. If I'm feeling brave I'll try the true hot-swap method. Think I'll test my backup between now and the reboot :)

Thanks for the info.

Dan
Uwe Zessin
Honored Contributor

Re: Does Creating an Array Erase Disks???

> I'd guess that the controller sets aside a small
> area of the disk for the controller info

Yes, that is why you can move complete disk drive arrays - because the controller can find out which disks belong together.
.
Dan Hawker
Advisor

Re: Does Creating an Array Erase Disks???


And indeed why it should be fine to move drives about without fear of data loss. If it only edits the array config part of the drive, surely the data on the disk(s) should be left intact.

Obviously this wouldn't be feasible in certain instances (moving part of a stripe or RAID5 about would obviously fail) however mirrors and stripes of single disks *should* be unaffected.

Or am I asking too much again :)

My reboot happens tomorrow, will post any results, good or bad...

Dan
Dan Hawker
Advisor

Re: Does Creating an Array Erase Disks???

Hi All,

Thanks for all your advice so far.

Basically, as mentioned I ended up going with the *insert drive, reboot, let the controller do its magic* method and I am glad to report it worked perfectly.

The controller did its job and sorted things and my host OS (FC5 x86_64, I decided to chuck it in a DL380 G4 x86_64 instead) displayed it as usual. I have since created a Xen VM with the drive and it is now back up and happily compiling something as we speak (once I did a setarch fudge of bash to make logons/apps believe it is an x86_32 machine).

Anyway, just reporting it worked as I'd hoped. As I'd organised a reboot there was no need to try the *live* method. Another time when I have some test data to try it on.

Thanks again

Dan
Dan Hawker
Advisor

Re: Does Creating an Array Erase Disks???

See above.
Michele Albrigo
New Member

Re: Does Creating an Array Erase Disks???

Bumping this up to ask some details...
My setup is:
Server A: ML370G3, SmartArray 642, 2x72gb raid 1 (Vol A1), 4x72gb raid 0+1 (Vol A2)
Server B: ML370G3, SmartArray 641, 2x72gb raid 1 (Vol B1), 2x72gb raid 1 (Vol B2)
The OS is Linux on both.

The operation I'd like to perform is moving Vol A2 to Server B, and moving Vol B2 to Server A, while keeping both Vol A1 and Vol B1 in place.

I always preserved the order of the disks in each operation, same disk in same slot, and I've always turned off the servers before moving disks. All operations of creation/deletion of volumes have been made from the SmartArray console (F8 at boot).

This is what I've done:
- take out Vol A2, took out Vol B2
- put Vol B2 into Server A, turned on Server A
- Server A didn't recognize the array on Vol B2
- take out Vol B2, deleted both arrays from Server A's controller, created array on Vol A1 disks (same settings) -> lost Vol A1 (I assume)
- put Vol A2 into Server B, Server B didn't recognize Vol A2 disks
- take out Vol A2, put Vol B2 back into Server B, Server B complained about a possible hardware failure, I told it to go on and now works fine (it just needed some reboots to go out of degraded mode, check filesystems etc.)
- put Vol A2 back into Server A, it recognized the array (still unable to boot, so I can't tell if there still are data on it, because Vol A1 was the OS partition).

Now the questions:
- can I assume that Vol A2 still has data on it?
- is there any way to accomplish my original objectives (moving Vol A2 to Server B and Vol B2 to Server A)? What should I do?

Next step I'd do would be the following:
- take out Vol B2
- delete the raid configuration for Vol B2 on Server B
- put Vol A2 into Server B
- pray for the autodetection to work fine

Is this the right thing to do?

Optionally I'd like to restore content on Vol A1, but that's not vital, since I can clone Server A from Server B quite easily (and Server A is going to be reinstalled anyway).

Thank you in advance!
Roy Main
Valued Contributor

Re: Does Creating an Array Erase Disks???

uh.... there should still be data on A2. Haven't seen anything you said that would have caused loss of data on that volume...

Here's the way I would try it - one change at a time.

Take B2 out and put it in Server A. Leaving the rest of Server A in it's original configuration. Only change is a new B2.

Then when all is well with Server A, remove A2 and move it to Server B. Follow the same steps.

The SA firmware should see the new disks and add them in using the configuration already on the disks.