Hard Disk IDs in Linux

Michael Torrie torriem at gmail.com
Tue Mar 12 18:13:28 MDT 2013

On 03/12/2013 01:30 PM, Lonnie Olson wrote:
> RAID6 can lose any 2 drives and still operate, so any 3 drives will
> cause complete failure.
> RAID10 will fail in as few as 2 drive failures, or as much as half of
> the array + 1.
> RAID10 has a better best case scenario failure rate, but a worse worst
> case scenario than RAID6.
> It may be unlikely, perhaps even very unlikely, for matched pairs to
> fail together, it still must be considered.
> This limitation can be mitigated with hot spares since they decrease
> the window of time the array is in a degraded state.  Also since
> RAID10 has a much quicker rebuild time, the window will be really
> small with a hot spare or two.

Yes Dan will likely want to have a number of hot spares for sure.

One thing to remember is that any time you increase the number of disks
in your array, no matter how you organize them to prevent data loss,
statistically, the odds of disk failure go up.  Though I've not
personally experienced losing 20 TB of data, I know that it can and does
happen no matter what kind of RAID you use.  Backup always has to be a
consideration when putting together large amounts of storage.

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