RAID member lost, OSX

How to use TestDisk to recover lost partition
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RAID member lost, OSX

#1 Post by nakedrabbit » 22 Mar 2013, 08:06

Hello, maybe you can help me with my problem. I sure hope so!

I have a 4.5Tb four disk RAID5 in an enclosure driven by a HighPoint RocketRAID 2314 card on a 2010 Mac Pro running OSX 10.6. Recently the volume spontaneously dismounted. At HighPoint's suggestion I deleted the RAID and set it up again without deleting data. This allowed me to recover about 200Gb of the material before it dismounted again.

High Point could not help me or tell me why my RAID was gone, but their WebGUI tool did tell me that two drives, #1 and #4, had too many bad blocks. I used dd to do a sector copy of both those drives onto two fresh ones. When I put them in the enclosure, the RAID began to rebuild itself. I let it run its course (possibly a mistake!) but the volume stll did not mount.

They recommended testdisk although they also freely admitted they had not used it and were going on previous customer recommendations. Let me say now that I am not a technician, I'm a video editor, so I am already quite confused by most of what is posted on this forum! But I have read through trying to understand...

Anyway, I physically loaded each dirve, one by one, into my Mac so I could use testdisk to check them. The reports for units 2,3 and 4 seem to be OK - I saw Mac HFS partitions as well as the volume name.

Unit #1 gave me the "disk too small" error. Here it is:

Disk /dev/disk3 - 1500 GB / 1397 GiB - 2930277168 sectors

The harddisk (1500 GB / 1397 GiB) seems too small! (< 6000 GB / 5588 GiB)
Check the harddisk size: HD jumpers settings, BIOS detection...

The following partitions can't be recovered:
Partition Start End Size in sectors
> Mac HFS 410336 8790082191 8789671856
Mac HFS 412792 8790084647 8789671856
Mac HFS 416432 8790088287 8789671856
Mac HFS 418120 8790089975 8789671856
Mac HFS 420528 8790092383 8789671856
Mac HFS 423616 8790095471 8789671856
Mac HFS 432296 8790104151 8789671856
Mac HFS 434440 8790106295 8789671856
Mac HFS 436984 8790108839 8789671856
Mac HFS 437024 8790108879 8789671856

It's the only one with that error - the rest seem to be completely fine - but then again, what would I know?

I've read about "adjusting the cylinders" when this error comes up, but I'll admit I'm at a loss to understand. Almost all of those threads are about single drives, not members of a RAID. My guess is that if I go to the "geometry" section and adjust them - then what? I'll be able to "see" the partition (which I can do already, btw) but then what do I do? This is a RAID5, so I'm assuming all my backup files are striped across the other drives. If I backed them up, what would I do with them then?

High Point seemed to think there was some way of "restoring the partition map" of the damaged member, and that this would allow me to recreate the array. But I'm over my head! Please, can anyone help?

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Re: RAID member lost, OSX

#2 Post by Fiona » 22 Mar 2013, 09:27

Do you have an Intel Mac or an old Power PC?
Intel Mac uses EFI GPT and the old Power Mac uses partition map.
Apple doesn't require any geometry.
That's why there are no changes to the geometry necessary.
To diagnose a RAID you need a fully functional array.
It must be recreated exactly like before.
Don't partition or format something.
Because you can use TestDisk to search for partitions.
You can use your cloned disk instead of the damaged one with the bad sectors.
If TestDisk finds your partition, using an Intel Mac, you can write your GPT-partition using testdisk.
If you're using Power PC and partition map, testdisk provides the results and you can use pdisk to get your partitions back.
Info about mac; ... 28Intel.29
Don't write anything to your disk, bcause it can make datarecover more difficult or impossible.


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Re: RAID member lost, OSX

#3 Post by nakedrabbit » 22 Mar 2013, 18:58

Thanks for the quick reply!

Yes, the Mac Pro is an Intel machine. Generally people will say "PowerMac" or "G5" when they mean an old PPC machine. And yes, I've seen testdisk identify the EFI GPT partition, so all seems well.

I have not changed any geometry. I only suggested that because several threads on this board did that when they got the "disk is too small" error, which I am getting on that drive.

When you say I need a "fully functioning array" does that mean that all four disks must be available to testdisk? The Mac Pro has only 4 internal SATA bays. I have been testing each one of the four disks one at a time in the machine, because testdisk cannot see the 4-drive enclosure through the RocketRAID card I normally use. Since the RocketRAID is what controls the 4 disks and makes them into a RAID, I'm not really sure what I'm going to get without it...

So is that what I would do?

I can put the drives back in the enclosure. I can try to connect the enclosure to the internal bus on the Mac Pro - I have one of those NewerTech devices that turns an internal SATA connecting into an external one. That would probably make the 4-drive enclosure available to testdisk.

Then what do I do? When you say that I can "write my GPT partition using testdisk" I am not quite sure what you mean - remember, I'm a dummy, and not a technician. Do you mean that I use testdisk to recover the entire 4.5Tb volume to some kind of other drive?

I'll go ahead and assemble the enclosure and see if I can at least get testdisk to see all four as I am predicting. Thanks for the help so far!

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Re: RAID member lost, OSX

#4 Post by nakedrabbit » 03 Apr 2013, 00:30

An update -

I've gone back and forth with HighPoint, the RAID card manufacturer, for almost a month now. I'm despondent.

The RAID has four elements. Disks 1 and 4 were the ones reporting bad blocks. They were cloned. They show up in Testdisk through the HighPoint RocketRaid 2314 card. Disks 2 and 3 do not. Testdisk will see them if I take them out of the enclosure and connect them to the internal SATA busses.

Highpoint suggests that if I can read the partition map of disk 1 or 4 and then write that same partition map to disk 2 and 3, I could save the RAID. Does this sound reasonable? How do I do this? I know how I can use testdisk to analyse a disk and then write the new partition map to the disk, but how do I write it to a file and then write that to a separate disk? Please help!

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Re: RAID member lost, OSX

#5 Post by nakedrabbit » 19 Jun 2013, 06:55

Final update. I gave up. No answers here, and no idea where to go next. I burned it all down and restored from backups - took several weeks.

Lots of dead ends.

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