HP LC2000r HP NetRAID 1M/2M Installation & Configuration - Page 22

Chapter 2 RAID Overview • Spanned arrays have logical drives that are spread across multiple arrays (as many as eight). This permits the physical drives in up to eight arrays to function as one large logical drive. Each spanned array must contain the same number of disks and all the disks in the logical drive must be connected to the same NetRAID adapter. Spanned array configurations use RAID levels 10 and 50. Arrays with No Redundancy: RAID Level 0 RAID 0: Striping In RAID 0 configurations, data is distributed among hard disks in the array via an algorithm called striping. Data written to a logical drive is divided into pieces called blocks. RAID 0 provides no data redundancy. If one hard disk fails, the data is lost from the entire logical drive and must be retrieved from a backup copy. If you have five physical drives configured as one RAID 0 logical drive, data blocks are written as follows: Disk 1 Disk 2 Disk 3 Disk 4 Disk 5 Stripe 1 Stripe 2 Block 1 Block 6 Block 2 Block 7 Block 3 Block 8 Block 4 Block 9 Block 5 Block 10 The RAID 0 algorithm allows data to be accessed on multiple disks simultaneously. Read and write performance on a multidisk RAID 0 system is significantly faster than on a single drive system. RAID 0 Advantages • Provides maximum data capacity, because all disk space is used for data. • Costs are low, because no disk space is allocated for redundancy. • Access time is fast for both reads and writes. RAID 0 Disadvantages • RAID 0 provides no redundancy so if a hard drive fails, data must be restored from backup. • Hot spares cannot be used with RAID 0 configurations. RAID 0 Summary • Choose RAID 0 if redundancy is not required, and you need fast performance and low costs. 14