Raid 5

Tyler Strickland tyler at
Fri Dec 2 14:07:34 MST 2005

On 12/02/2005 01:57 PM, Nicholas Leippe wrote:
> If you consider as I do, that the first drive failure is a given,
> then the odds of failure is magnitudes larger--back up to the same order
> of magnitude as a single drive failing.
> This makes the relative differences in failure odds become significant,
> especially when you consider how the odds increase with additional capacity.

What you say is true about the probability increasing with a failed 
drive.  The probability of two drives failing at once is very small, but 
the probability of a second drive failure after the first has occurred 
is much larger.  RAID 10 can, in most cases, survive multiple failures, 
while a RAID 5 cannot. So our lesson for today, kids, is "Always fix 
your degraded array as quickly as possible."

As a related side note, hot spares are a wonderful thing...


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