On 11/21/2013 3:07 AM, David Brown wrote: > For example, with 20 disks at 1 TB each, you can have: All correct, and these are maximum redundancies. Maximum: > raid5 = 19TB, 1 disk redundancy > raid6 = 18TB, 2 disk redundancy > raid6.3 = 17TB, 3 disk redundancy > raid6.4 = 16TB, 4 disk redundancy > raid6.5 = 15TB, 5 disk redundancy These are not fully correct, because only the minimums are stated. With any mirror based array one can lose half the disks as long as no two are in one mirror. The probability of a pair failing together is very low, and this probability decreases even further as the number of drives in the array increases. This is one of the many reasons RAID 10 has been so popular for so many years. Minimum: > raid10 = 10TB, 1 disk redundancy > raid15 = 8TB, 3 disk redundancy > raid16 = 6TB, 5 disk redundancy Maximum: RAID 10 = 10 disk redundancy RAID 15 = 11 disk redundancy RAID 16 = 12 disk redundancy Range: RAID 10 = 1-10 disk redundancy RAID 15 = 3-11 disk redundancy RAID 16 = 5-12 disk redundancy -- Stan -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
