User`s guide
Table Of Contents
- About This Guide
- Kit Contents and System Requirements
- About Your RAID Controller
- Standard RAID Controller Features
- Adding Enhanced Features
- Adding a Battery Backup Module
- Upgrading the Controller Firmware
- About the Adaptec 3085
- About the Adaptec 3405
- About the Adaptec 3805
- About the Adaptec 31205
- About the Adaptec 31605
- About the Adaptec 4000
- About the Adaptec 4800SAS
- About the Adaptec 4805SAS
- About the Adaptec 2420SA
- About the Adaptec 2820SA
- About the Adaptec 2130SLP
- About the Adaptec 2230SLP
- Getting Started
- Installing the Controller and Disk Drives
- Creating a Bootable Array
- Installing the Driver and an Operating System
- Installing the Driver on an Existing Operating System
- Managing Your Storage Space
- Solving Problems
- Introduction to Serial Attached SCSI
- Understanding RAID
- Using the Adaptec RAID Configuration Utility
- Using the Array Configuration Utility for DOS
- Using the Adaptec Flash Utility
- Adaptec Serial Controller LED and I2C Connector Reference
- Adaptec 2420SA Activity LED and I2C Connector Specification
- Adaptec 2820SA Activity LED and I2C Connector Specification
- Adaptec 3085 LED and I2C Connector Specification
- Adaptec 3405 LED and I2C Connector Specification
- Adaptec 3805 LED and I2C Connector Specification
- Adaptec 31205 LED and I2C Connector Specification
- Adaptec 31605 LED and I2C Connector Specification
- Adaptec 4800SAS LED and I2C Connector Specification
- Adaptec 4805SAS LED and I2C Connector Specification
- Safety Information
- Technical Specifications
- Index
Appendix B: Understanding RAID ● 79
RAID 5 Arrays
A RAID 5 array is built from a minimum of three disk drives, and uses data striping and parity
data to provide redundancy. Parity data provides data protection, and striping improves
performance.
Parity data is an error-correcting redundancy that’s used to re-create data if a disk drive fails.
In RAID 5 arrays, parity data (represented by Ps in the next figure) is striped evenly across the
disk drives with the stored data.
Drive segment size is limited to the size of the smallest disk drive in the array. For instance, an
array with two 250 GB disk drives and two 400 GB disk drives can contain 750 GB of stored
data and 250 GB of parity data, as shown in this figure.
Disk Drive 1
Disk Drive 2
Disk Drive 3
Disk Drive 4
250 GB
250 GB
400 GB
400 GB
Drive Segment Size
(Smallest Disk Drive)
Disk Drive 2
Disk Drive 3
Disk Drive 4
Disk Drive 1
1 4 ... P
2 5 ... 748
3 P ... 749
P 6 ... 750
Unused Space = 150 GB
Disk Drives in Logical Drive RAID 5 Logical Drive = 750 GB plus Parity
Unused Space = 150 GB