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I have a Synology NAS that I've set up with RAID 1. The device is set up with two drives, both the same size (i.e. 500 GB each), formatted in ext3, as a RAID 1 volume (i.e. even though the total capacity is 1TB, I effectively only get 500 GB).

In the case of a device failure where I can only access one of the drives, how can I recover my data? The solution I'm looking for is something like: 'Put the working drive in an enclosure, and use <some software> to recover your data.'

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So you have a RAID1 comprised of two 500GB drives. In a RAID1, each individual drive is an exact copy of every other drive in the array. (That's why a RAID1 is also called a mirror.) One of the great benefits of RAID1 is that as long as at least one drive in the array is good, your array remains alive and accessible.

So your question is moot. In the case of a single drive failure in a 2-drive RAID1, your array is still good (albeit in a "degraded" state), so you don't have to do anything special to recover your data. You should still be able to access the data as you would normally do.

That said, whenever a drive in a RAID array fails, you really do need to replace that drive with a good drive, and then "resync" the array, as soon as possible. Most RAID appliances I'm aware of automatically initiate a "resync" whenever a new drive has replaced a failed one. Furthermore, during a resync, the array should remain alive and accessible (although probably slower).

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You've affirmed the fundamental concept behind RAID1, which I understand, but I still don't know how to get at the data. I have MacFUSE installed with the fuse-ext2 pref which lets me mount ext2/3 volumes but MacOSX still doesn't see my RAID1 volume. Do you have any suggestions for pieces of software to recover? – Avery Chan Apr 25 '12 at 12:41

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