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I have a server that was running two 60GB drives as a logical RAID1. At some point the second drive was physically removed and the logical drive has been in "Interim Recovery Mode" for several months now.

There's no need for the redundancy of RAID1 on this machine, and I have no intention of replacing the missing drive. If possible I would like to convert the current RAID1 to a single-drive RAID0 by simply dropping the failed drive from the current configuration.

I'm only interested in doing this if it can be done in-place. Otherwise I'm perfectly content to leave it in "Interim Recovery Mode" indefinitely.

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I know on a DL360G5, you can't turn a RAID0 into a RAID1, don't know about the converse. – sysadmin1138 Dec 1 '10 at 6:34
Don't you really want to go from a RAID1 -> JBOD? Not sure why you bring up a RAID0. – Zoredache Dec 1 '10 at 7:22

Yes, it can be done (depending on the controller). You may need the "HP Smart Array Advanced Pack" ($$).

HP calls RAID1->0 "mirror splitting."

Smart Array Advanced Pack is hosted on the Smart Array Controller hardware and can be enabled on the HP Smart Array P212, P410, P410i, and P411 controllers with a Battery Backed Write Cache module or a Flash Backed Write Cache module.. SAAP functionality is standard on the HP Smart Array P812 controller.

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If you have no intention of replacing the drive, why go through the effort of changing the RAID level, even if your controller supports it?

RAID1 doesn't involve parity, so there's no computational overhead. If you know it's failed and you don't care, just leave it.

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RAID by definition implies an array of disks. So there can't be any type of RAID with just 1 disk drive.

RAID0 is about striping a set of drives for better performance.

RAID1 is about mirroring contents of 1 or more drives onto a similar set of drives.

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I think he's made it clear that he understands this distinction, and will leave the machine running with one of the two RAID1 disks intact, but would like to convert to RAID 0 and reformat / replace the second drive if possible. – user3914 Dec 1 '10 at 5:39

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