HP LH4r Integrated HP NetRaid Controller Configuration Guide - Page 20

Chapter 2 RAID Overview Spanned Arrays: RAID Levels 10, 30, and 50 Array spanning allows the capacity of two, three, or four arrays to be combined into a single storage space. A spanned array configuration must have the same number of disk drives in each array: each array can have two disks, three disks, four disks, and so on. RAID 10: Spanning with Mirrored Arrays A RAID 10 configuration uses two, three, or four pairs of mirrored disks, spanning two, three, or four arrays, respectively. (RAID 10 is a RAID 1 configuration with array spanning.) If your RAID 10 logical drive spans two arrays with two physical drives each, data blocks are written as follows: Array 1 Array 2 Stripe 1 Stripe 2 Stripe 3 Disk 1 Block 1 Block 3 Block 5 Disk 2 Block 1 Block 3 Block 5 Disk 3 Block 2 Block 4 Block 6 Disk 4 Block 2 Block 4 Block 6 RAID 10 Advantages There is no data loss or system interruption due to disk failure, because if one disk fails, its mirror image is available. Read performance is fast, because data is available from either disk in each pair. RAID 10 lets you create large logical drives. You can span up to four arrays containing a maximum of eight physical drives. RAID 10 Disadvantages Costs are high, because 50% of all disk space is allocated for redundancy. Capacity expansion is an offline operation only. RAID 10 Summary RAID 10 provides the best performance for most applications where redundancy and large logical drive size are required, and cost is not a factor. 14