User guide
Table Of Contents
- MSA1000 User Guide
- Contents
- About this Guide
- Chapter 1: Introduction
- Chapter 2: Operating System Specific Information
- Chapter 3: MSA1000 Setup and Sample Configurations
- Chapter 4: Operation and Management
- Chapter 5: Array Configuration Utility (ACU)
- Installing the ACU on the Server
- Accessing the ACU
- Description of Screen Regions
- Configuring a New Controller
- Modifying an Existing Controller
- Probability of Logical Drive Failure
- Chapter 6: Command Line Interface (CLI)
- CLI Overview
- CLI Setup
- Help Commands
- Display Commands
- Array Controller Configuration Commands
- LUN Management Commands
- Server Connection Commands
- Selective Storage Presentation/Access Control List Commands
- Appendix A: Regulatory Compliance Notices
- Appendix B: Electrostatic Discharge
- Appendix C: Specifications
- Appendix D: Hard Drive Arrays
- Appendix E: Recovering from Hard Drive Failure
- Appendix F: Controller Display Messages
- Appendix G: Recovery ROM and ROM Cloning
- Appendix H: SCSI ID Assignments
- Index
Hard Drive Arrays
175Modular SAN Array 1000 User Guide
Drive failure, although rare, is potentially catastrophic. In Figure 64, for example,
failure of any physical drive causes all logical drives in the same array to fail, and
all data on the drives is lost.
To protect against data loss due to physical drive failure, logical drives are
configured with fault tolerance. There are several fault-tolerance methods; those
described in the following section are:
■ RAID 0—Data Striping only (no fault tolerance)
■ RAID 1—Drive Mirroring
■ RAID 1+0—Data Striping and Drive Mirroring
■ RAID 5—Distributed Data Guarding
■ RAID ADG—Advanced Data Guarding
For any configuration except RAID 0, further protection against data loss can be
achieved by assigning a drive as an online spare (or hot spare). This drive
contains no data and is connected to the same controller as the array. When any
other physical drive in the array fails, the controller automatically rebuilds
information that was originally on the failed drive to the online spare. The system
is quickly restored to full RAID-level data protection. (However, in the unlikely
event that another drive in the array fails while data is being rewritten to the spare,
the logical drive will still fail.)
When you configure an online spare, it is automatically assigned to all logical
drives in the same array. Additionally, you do not need to assign a separate online
spare to each array; you can configure one hard drive to be the online spare for
several arrays, as long as the arrays are all on the same controller.
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