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I've read "on the interwebs" that Raid is starting to become an inadequate solution with todays large disks. As I've understood it, the rebuild time and the risks for rebuild failures are very problematic.

This might be a fuzzy question, but are there better alternatives than RAID1 to mirror 2x 2TB disks in 2012? If not, I will use md.

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You can add this link to the "on the interwebs"part. It gives a nice clear explanation why some RAID levels should not be used for some tasks. Also note that the RAID 1 section has no negative information on rebuilding. which for RAID1 is a relative simple process. Link:… – Hennes Aug 31 '12 at 14:52
up vote 3 down vote accepted

The general consensus is that RAID5 rebulid times are getting quite high for large RAID 5 volumes. During rebuilds the drives can be quite stressed and rebuilds may fail if another drive has any URE's (unrecoverable read errors). It's better to think of probablity of URE's rising with the overall RAID volume size rather than number of drives which is why this issue is being considered more and more with todays large drive sizes.

The typical method to defeat this is to employ RAID 1/10/6/60.

RAID 5 is slower than RAID 1 or 10 for rebuilds due to the parity calculations. RAID 6 and 60 are also hampered by these issues but can tolerate another drive dropping during the stressful rebuild so the problem isn't quite so bad.

In your situation the rebuild time shouldn't be too bad, but software RAID controllers aren't great. If you really depend on your data I would recommend a hardware RAID controller with battery backed cache. This way even if you had a power cut as data was being written, any data committed to the RAID controllers cache would be preserved by the battery to be written to the drives when power is restored.

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Are both "software RAID controllers" and "Linux sw raid" not great? – Znarkus Aug 31 '12 at 9:19
Never used Linux sw RAID myself so can't comment on anything except it won't use a battery backed cache. I've had some bad experiences with software RAID controllers (on supported OS's) that have made me never want to use one again. – Robin Gill Aug 31 '12 at 12:01
@znarkus Linux software RAID is actually pretty decent. I'd prefer a hardware RAID controller, but have yet to see any problems caused by the native software RAID in Linux. – HopelessN00b Aug 31 '12 at 13:41

What you've probably read is that RAID5 is an inadequate solution for large drives in large arrays when using consumer grade equipment because the number of operations required to rebuild exceeds the unrecoverable read error rate for such drives.

RAID1 is fine with those size drives.

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