Chapter 1 : " Introduction " This chapter will introduce you to your new Disk Array's features and provide information on general RAID concept.
Introduction Features This section provides an overview of the features. For more detailed information, please refer to the technical specifications appendix at the end of this manual . Your Disk Array includes the following features : Easy Operation As everyone knows, conventional Disk Arrays are designed for experienced computer specialists.
Solid reliability Automatic failed disk drive detection. Auto rebuild : when a replacement disk installed (or by using hot spare disk ), The system provides automatic data rebuild without any commands or functions keyed in. ( Transparent to Host ) Efficient maintenance An LCD status panel displays a comprehensive readout of the operating status, and the HDD LED indicators on each HDD tray display the individual HDD status.
Introduction General RAID Concepts Correct installation of the disk array requires an understanding of RAID technology and the concepts described in this section. Definition RAID is an acronym of Redundant Array of Independent Disks . A RAID is a Disk Array in which part of the storage capacity is used to record redundant information about the user data stored on the remainder of the storage capacity.
Introduction RAID Levels RAID Level 0 : " Disk Striping " High I/O Performance 4 6 5 7 8 9 10 3 Data 2 11 12 1 Disk Array Controller Array Management Software Provides Logical to Physical Mapping 1 5 2 6 3 7 4 8 Disk 1 Disk 2 Disk 3 Disk 4 Physical Improved I/O performance is the major reason for using RAID level 0. No protection is provided against data loss due to member disk failures.
Introduction RAID level 0 arrays are not particularly suitable for : Applications which make sequential requests for small amount of data. These applications will spend most of their I/O time waiting for disks to spin, whether or not they use striped arrays as storage media. Applications which make synchronous random requests for small amounts of data.
Introduction RAID Level 1 : " Disk Mirroring " High Data reliability 4 6 5 7 8 9 10 3 Data 2 11 12 1 Disk Array Controller Array Management Software Provides Logical to Physical Mapping 1 2 3 1 2 3 1 2 3 1 2 3 Disk 1 Disk 2 Disk 3 Disk 4 Physical Optional RAID level 1 provides both very high data reliability and continued data availability in the event of a failure of an array member.
Introduction RAID Level 3 : " Parallel Transfer Disks with Parity " High Data Reliability & Highest Transfer Capacity 4 6 5 7 8 9 10 3 Data 2 11 12 1 Disk Array Controller Array Management Software Provides Logical to Physical Mapping 1 4 7 2 5 8 3 6 9 P P P Disk 1 Disk 2 Disk 3 Disk 4 Physical P : Parity RAID Level 3 technology use a dedicated parity disk to store redundant information about the data on several data disks.
Introduction The distinctive performance characteristics of RAID Level 3 : RAID Level 3 provides excellent performance for data transfer-intensive applications. RAID level 3 in not well suited for transaction processing or other I/O request-intensive applications.
Introduction RAID Level 5 : " Independent Access Array with Rotating Parity " High Data Reliability & Transfer Capacity 4 6 5 7 8 9 10 3 Data 2 11 12 1 Disk Array Controller Array Management Software Provides Logical to Physical Mapping 1 4 7 2 5 P 3 P 8 P 6 9 Disk 1 Disk 2 Disk 3 Disk 4 Physical P : Parity When RAID Level 5 technology is combined with cache memory to improve its write performance, the result can be used in any applications where general purpose disks would be suitabl
Introduction RAID level 5 arrays have unique performance characteristics : The data can be recalculated or regenerated, using parity, when any drive in the array fails. When the failed drive is replaced, either automatically if the subsystem contained a hot spare drive, or by user intervention during a scheduled maintenance period, the system will be restored its full data redundancy configuration by rebuilding all of the data that had been stored on the failed drive onto the new drive.
Introduction Summary Comparison of RAID Levels RAID Level Common Name 0 Disk Striping 1 Mirroring 3 Parallel Transfer Disks with Parity 5 Independent Access Array with Rotating Parity Description Data distributed across the disks in the array. No redundant Information provided. Array's Data Capacity Reliability Data Transfer Capacity (N) disks Low Very High All data Duplicated 1*disk Ver y High High Data sector is subdivided and distributed across all data disk.
Introduction Supported RAID Levels Based on the needs of a Disk Array's capacity, data availability, and overall performance, you can select a proper RAID level for your Disk Array. The supported RAID levels are shown in below : RAID Level 0 1 3 5 Function Description "Disk Striping" , block striping is used, which yields higher performance than with the individual disk drives. * There is no redundant function.
