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RAID1 and protection against filesystem corruption?

Posted on 2014-02-17
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Last Modified: 2014-02-18
We ship RAID1 systems to our customers (two drives, using Win7 dynamic disk)
We thought (perhaps naively) that this would protect a customer's data if one drive fails.  

We had a system in the field that would no longer boot - bluescreen, flash, restart, repeat.

No idea of root cause. We pulled both drives, and they are both exactly the same, with the same set of corrupted files (windows fails to copy many of them, chkdsk fails to fix them).   I was very surprised by this, I would have thought if "junk" were written to one, it wouldn't propagate, but I guess that was incorrect thinking.  

I believe the RAID1 configuration would have "worked" if one drive had physically failed, but I suppose there is a big difference between a physical failure and data integrity. How could I have prevented this scenario where the filesystem on both drives was effectively corrupted at the same time?
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Question by:PMH4514
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Beartlaoi earned 2000 total points
ID: 39865122
In a RAID1 mirror you cannot prevent both drives from being written to with the same data as that exactly contradicts what RAID1 does.  It only protects you from hardware failure by making sure that both drives are identical so that either can be used if one fails.
If something running in the OS decides to write something to the disk that corrupts it, then no RAID system will protect you from that.
Luckily Windows has several mechanisms in place to help you in this scenario.
Last known good boot, safe mode, system restore points, the recovery options on the setup DVD, and backups can be used to recover a system.
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by:Gerald Connolly
ID: 39866785
RAID-1 is also-known-as Mirroring, thats the clue that the filesystem on both disks will be corrupted simultaneously.

The only way to protect from file system corruption is backups.
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Author Comment

by:PMH4514
ID: 39867156
Thanks, makes perfect sense.
Unfortunately  the last known good and repair options didn't work. turns out there was a suitable backup, so it wasn't the end of the world.
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