[mythtv-users] 2 TB Hard Drive Recommendations

Kevin Ross kevin at familyross.net
Mon Dec 6 19:20:37 UTC 2010

On 12/06/2010 07:28 AM, Fedor Pikus wrote:
> Do not use RAID5 with disks over 1TB. Use RAID6. The probability of
> disk error while reading the whole disk is so high that it is very
> likely that after replacing a failed disk the array will fail to
> reconstruct. In RAID5 second fault, even transient, destroys the
> array.

This isn't 100% true.  You aren't likely to lose the entire array, just 
a few files.  I've had it happen to me. When the second drive starts 
dropping out of the array during a rebuild, you copy that drive using 
ddrescue to a new drive, put the new drive in the array replacing the 
old one, and let it rebuild.  Any bad sectors that ddrescue couldn't 
recover will be replaced with 0's.  This could be in the middle of a 
file, or in filesystem metadata, or completely unused space.  Run an 
fsck (or equivalent) after the rebuild to fix filesystem metadata.  If 
you're using a filesystem that keeps checksums of files, like ZFS or 
BtrFS, then you'll know which files have become corrupt.

Obviously this isn't ideal, but being able to recover as much data as 
possible is better than losing the entire array.

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