Artículo interesante sobre niveles de RAID

He encontrado este artículo, donde se discute acerca de los niveles de RAID, y el riesgo de RAID 5 y RAID 6, y la conveniencia o no de HotSpare. Después de leerlo, estoy bastante de acuerdo con el autor, y me hace replantearme algunos conceptos acerca de este tema, sobretodo de la gente, como yo, que trabaja en entorno SMB. Os adjunto link

http://www.smbitjournal.com/2012/07/hot-spare-or-a-hot-mess/

Especialmente, el problema viene cuando :

UREs don’t cause healthy arrays to fail because either parity or mirroring contains the same bit elsewhere and can reconstruct the data without issue. It is only in a degraded parity array (where there is no longer any parity) that the URE causes a full array failure and this is because during a resilver operation the array is unstable and when a URE is encountered the parity is unable to reconstruct the stripe and the resilver fails causing the array itself to fail.

UREs, in the real world during a parity resilver, really do cause a complete loss of the array. It’s catastrophic level failure.

Mirrored RAID (RAID 1 or RAID 10, for example) does not do a computation to reconstruct a stripe and so a URE does not cause a resilver to fail. It is specifically parity reconstruction + URE that is the danger.