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 ● 77
RAID 1 Arrays
A RAID 1 array is built from two disk drives, where one disk drive is a mirror of the other (the
same data is stored on each disk drive). Compared to independent disk drives, RAID 1 arrays
provide improved performance, with twice the read rate and an equal write rate of single disks.
However, capacity is only 50 percent of independent disk drives.
If the RAID 1 array is built from different- sized disk drives, the free space, drive segment size is
the size of the smaller disk drive, as shown in this figure.
RAID 1 Enhanced Arrays
A RAID 1 Enhanced (RAID 1E) array—also known as a striped mirror—is similar to a RAID 1
array except that data is both mirrored and striped, and more disk drives can be included. A
RAID 1E array can be built from three or more disk drives.
In this example, the large bold numbers represent the striped data, and the smaller, non-bold
numbers represent the mirrored data stripes.
Disk Drive 2
Disk Drive 1 250 GB
400 GB
Drive Segment Size
(Smallest Disk Drive)
Disk Drive 1
Disk Drive 2
Disk Drives in Logical Drive
RAID 1 Logical Drive = 250 GB
1 – 250
1 – 250
Unused Space = 150 GB
Disk Drive 2
Disk Drive 1
400 GB
Disk Drives in Logical Drive RAID 1E Logical Drive = 600 GB
400 GB
400 GBDisk Drive 3
Disk Drive 2
Disk Drive 1
Disk Drive 3
1 3
2
3
4
5
6
1
2
6
4
5