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Possibly recover a missing RAID stripe? orr mirror?
Authored by: Shawn Parr on Jul 18, '05 01:09:15PM

Actually they state that they initialized the Partition Map, not that they formatted the drive. Initializing the Partition Map theoretically should not affect any of the data.

It was a bit confusing to state that the Partition information was 'mirrored' as while this may be correct, is probably inadvisable in a discussion on striped RAID systems.

If it was a mirrored RAID system it would not have disappeared in the first place, as a mirror is designed so that with a drive failure you will still be up and running. A full format, and RAID rebuild would have been all that was necessary to fix the RAID.

I have dealt with similar issues in Linux systems, where the partition map gets hosed somehow, and with luck one can initialize the Partition Map and try to set things right again. Not fun if you don't have an identical drive to work with though...



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Possibly recover a missing RAID stripe? orr mirror?
Authored by: nhl00 on Jul 18, '05 10:54:12PM

I have two external firewire drives set up as a RAID mirror. One of them is no longer being recognized as part of the RAID. The whole reason for my chosing this set up was to get a level of protection for my photos.

I'm curious if you could elaborate on your comments on how to restore the mirror in this case (as opposed to the stripe).

I should point out that I don't know how long ago the RAID stopped being a RAID and therefore must assume that the missing drive is not up to date with the data on the functioning half.

Thanks
Frank



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Possibly recover a missing RAID stripe? orr mirror?
Authored by: Shawn Parr on Jul 19, '05 11:44:38PM

On the drive that is no longer being recognized, use Disk Utility to format it as a Unix disk (this seems to clear out more low level info than an HFS type format).

Then format it so that it looks like the other disk partition & format-wise.

Then use Disk Utility to rebuild the RAID. I am sorry I don't have in-depth info for this as I don't have any software RAID's currently.

As a side note, I had a Mac OS X Server set up using a Disk Utility RAID1 mirror for a while. Turns out that it also lost sync between the disks, and later on the remaining disk became corrupted. One rebuild later and I convinced the department I was working for to get a hardware unit. In this case it was the eRAID from Firewire depot. Any failures and there is an alarm and LEDs to diagnose. Much better than a software RAID IMHO. We unfortunately had a drive failure 2 weeks after we installed the RAID, but due to it being RAID5 we lost no uptime, and were immediately notified by the audible alarm.

Quite frankly if I am concerned enough about my data being reliable, I would never trust a software RAID system. Backup is much more reliable, and if you need all that online and reliable hardware RAID is the only real solution.



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Possibly recover a missing RAID stripe? orr mirror?
Authored by: nhl00 on Jul 21, '05 12:39:03AM

Cheers for the details...

The eRAID box looks interesting, but is outside of my budget - this is for my personal photo collection not work. I do keep a back up, the idea of setting up a RAID mirror was to catch a drive failure between backups.

Frank



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