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Helpful answers
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Nov 19, 2013 7:33 PM in response to jebediasby Grant Bennet-Alder,Launch Disk Utility.
Inspect the RAID Volume to see which drive has failed, or just look in the list on the left and one of component drive slices will say "failed".
You can erase that slice and Write Zeroes to it. If you find yourself doing that again soon, that drive needs to be replaced, and the old drive re-purposed for light duty only. [Do not just keep re-zeroing that drive, you are only fooling yourself -- the idea is maximum uptime and low mean-time-to-repair, and a falling drive does not deliver that.]
Writting Zeroes will cause the drive controller to substitute spare blocks (that it has in reserve) for any Blocks found Bad after being written. This will reduce re-trys and help your drives stay together.
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Nov 22, 2013 3:25 PM in response to Grant Bennet-Alderby jebedias,It happened two times in a day, about a week ago, and never again since then.
I did use less the drive after backing everything up.
How can I write zeroes in it?
And in case the raid doesn't fail again, how can I be certain of which disk was the bad one? Disk Utility won't check for a surface scan...
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Nov 22, 2013 5:14 PM in response to jebediasby Grant Bennet-Alder,Launch Disk Utility and Select the RAID, and click the RAID Heading.
On the RAID pane, the RAID will show its component drives.
When the RAID status is Degraded, one drive remains online, the other will be offline or failed. Click on the drive that is offline or failed. That should also highlight which drive that is in the list on the left. Click the drive in the list on the left and you should be able to determine which bay it is in.
You do not have to Zero it each time, you can simply Rebuild the array. Rebuild is a more drastic approach to ensure the drive is working -- rather than a surface SCAN, it is more like a surface repair.