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
Recovering from Hard Drive Failure
184 Modular SAN Array 1000 User Guide
Hard Drive Failure
When a hard drive fails, all logical drives that are in the same array will be
affected. Each logical drive in an array may be using a different fault tolerance
method, so each logical drive can be affected differently.
■ RAID 0 configurations cannot tolerate drive failure. If any physical drive in
the array fails, all non-fault-tolerant (RAID 0) logical drives in the same array
will also be failed.
■ RAID 1 and RAID 1+0 configurations can tolerate multiple drive failures, as
long as none of the failed drives are mirrored to one another.
■ RAID 5 configurations can tolerate one drive failure.
■ RAID ADG configurations can tolerate simultaneous failure of two drives in
the array.
■ Spare hard drive configuration guidelines include:
— A spare must be assigned to each individual array separately.
— A spare must be greater than or equal to any drive that it is intended to
replace.
— The same spare can be assigned to multiple Controllers as long as its
capacity is greater than or equal to any drives in that array.
Note: Only remove hard drives that have been failed or marked as degraded by the
Controller.
If more hard drives are failed than the fault-tolerance method allows, fault
tolerance is “compromised” and the logical drive is failed. In this case, all requests
from the operating system will be rejected with “unrecoverable” errors. The
section on Compromised Fault Tolerance later in this chapter discusses possible
ways to recover from this situation.
230941-005_MSA1000_UG.book Page 184 Thursday, April 17, 2003 5:53 PM