3Ware 720-0127-02 Manual

Also see for 9500S: Cli guide Guide Guide User guide

Contents

3Ware 720-0127-02 Manual Manual pdf 18 page image

Chapter 1. Introduction to the 3ware Command Line Interface10 3ware 9000 Series Serial ATA Controller CLI GuideUnderstanding RAID Concepts and LevelsThe next few pages introduce RAID concepts you may find useful. Foradditional information about installing and managing your 3ware controller,see the user guide that came with your 3wae RAID controller.3ware controllers use a Redundant Array of Inexpensive Disks (RAID) toincrease your storage system’s performance and provide fault tolerance(protection against data loss).The following concepts are important to understand when working with aRAID controller: Arrays and Units. In the storage industry, the term “array” is used todescribe two or more disk drives that appear to the operating system as asingle unit. When you work with 3ware software, “unit” is the term usedto refer to an array of disks that is configured and managed through the3ware software. Single-disk units can also be configured in the 3waresoftware. Mirroring. Mirrored arrays write data to paired drives simultaneously. Ifone drive fails, the data is preserved on the paired drive. Mirroringprovides data protection through redundancy. In addition, mirroring usinga 3ware controller provides improved performance because 3ware’sTwinStor technology reads from both drives simultaneously. Striping. Striping across disks allows data to be written and accessed onmore than one drive, at the same time. Striping combines each drive’scapacity into one large volume. Striped disk arrays achieve highesttransfer rates and performance at the expense of fault tolerance. Distributed Parity. Parity works in combination with striping on RAID 5and RAID 50. Parity information is written to each of the striped drives,in rotation. Should a failure occur, the data on the failed drive can bereconstructed from the data on the other drives. Hot Swap. The process of swapping out a drive without having to shutdown the system. This is useful when you need to swap out a degradeddrive, manually or automatically, with a pre-designated spare. Array Roaming. The process of swapping out or swapping in aconfigured unit without having to shut down the system. This is useful ifyou need to move the unit to another controller. Disk Roaming. The process of removing a unit from a controller andputting it back later, either on the same controller, or a different one, andhaving it recognized as a unit. The disks may be in a different order thanthey initially occupied, without harm to the data. The disks may beattached to the same ports or different ports on the controller.