Basic Disk Configuration Concepts. Netgear ReadyNAS NV+ v2, RND4475 - ReadyNAS NV+ NAS Server, Home RAIDiator 5.3, ReadyNAS Duo v2

ReadyNAS for Home RAIDiator 5.3

Basic Disk Configuration Concepts

To get the most out of your ReadyNAS storage system, it is helpful to understand some disk configuration concepts. Understanding these concepts is the first step to making good decisions about how to configure, manage, and use your ReadyNAS storage system.

You can configure your storage system’s hard disks in a variety of ways. The most common way to configure disks is using one of the many RAID technologies.

RAID

RAID is short for redundant array of independent disks. RAID is a storage technology that balances data protection, system performance, and storage space by determining how the storage system distributes data. Many different ways of distributing data have been standardized into various RAID levels. Each RAID level offers a tradeoff of data protection, system performance, and storage space. For example, one RAID level might improve data protection but reduce storage space. Another RAID level might increase storage space but also reduce system performance.

Your ReadyNAS storage system supports X-RAID2

TM

, a proprietary single-volume RAID architecture that is easy to administer, and Flex-RAID, which allows you to format your disks in a variety of industry-standard RAID levels.

Volumes

In the most general sense, volumes are data storage devices. Your computer treats an internal hard drive as a volume. It also treats a portable USB thumb drive as a volume.

Volumes can be either physical or logical. Usually, the term physical volume refers to a hard disk drive. When this term is used in this way, a two-bay storage system can have up to two physical volumes (hard disk drives), a four-bay storage system can have up to four physical volumes, and a six-bay storage system can have up to six physical volumes.

The term logical volume refers to the way that you divide, or partition, your storage space, for example:

•

Each logical volume can correspond to a hard disk drive.

•

A logical volume can be made up of more than one hard disk drive.

In this manual, the term volume refers to a logical volume and the terms hard disk drive and

disk refer to a physical volume.

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ReadyNAS for Home RAIDiator 5.3

X-RAID2

X-RAID2 is a RAID technology that expands automatically and is available only on

ReadyNAS systems. With X-RAID2, you do not need to know intricate details about RAID to administer your system. X-RAID2 allows you to add storage space without reformatting your drives or moving your data to another location. Because the expansion happens online, you can continue to use your ReadyNAS system while the underlying volume capacity increases.

Because X-RAID2 uses a single-volume architecture, if you configure your hard disk drives to use X-RAID2, your storage system has only one volume that is made up of all installed hard disk drives. X-RAID2’s single-volume architecture has two major advantages:

•

Easy system management

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Auto expansion

With typical RAID formatting, if you want to add disks or replace disks with larger capacity disks, you must back up the data to another system, add a new disk, reformat the RAID volume, and restore the data to the new RAID volume. With X-RAID2, none of those administrative tasks are required. Instead, with X-RAID2, your volume automatically expands to accommodate additional disks or larger capacity disks when you replace smaller capacity disks.

With X-RAID2, you can start out with one hard disk, add a second disk for data protection, then add more disks for additional capacity, and X-RAID2 accommodates the new disks automatically. You can replace existing disks with larger capacity disks and X-RAID2 automatically accommodates the new disks.

X-RAID2 requires a minimum of two hard disks to provide protection against disk failure. If you have a one-disk X-RAID2 storage system and want protection from disk failure, you must add a second disk that is at least as large as the first. It can be added while the system is running.

X-RAID2 uses the first disk to store data, and the second disk to store parity information that allows it to re-create data if a disk fails. This means that in a two-disk system, the usable storage space is one disk. In a three-disk system, the usable storage space is two disks, and in a four-disk volume, the usable storage space is three disks.

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ReadyNAS for Home RAIDiator 5.3

The following figure illustrates how X-RAID2 uses new disks.

1

2

3

Figure 5. X-RAID2 disk usage

1. Initial storage space

2. Data protection

3. Additional storage space

Flex-RAID

NETGEAR’s Flex-RAID technology allows you to choose from among several industry-standard RAID levels:

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RAID 0. This is the simplest RAID level, and is misnamed, because it does not offer redundancy to protect your data from loss if one disk fails. RAID 0 distributes data across multiple disks, which allows it to offer better performance than disks that do not use RAID formatting. The total capacity of your storage system equals the capacity of all of your disk drives.

•

RAID 1. This RAID level provides full redundancy of your data, because it duplicates data across multiple disks. In RAID 1, exactly the same data is stored on two or more disks at all times. RAID 1 protects your data from loss if one disk fails. RAID 1 requires a minimum of two disks and an even number of disks. In a two-disk system, the total capacity of your storage system equals the capacity of your smallest disk.

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RAID 5. Supported on ReadyNAS storage systems with at least four drive bays, RAID 5 uses one disk to protect you from data loss if one disk fails. The total capacity of your storage system equals the capacity of all your disks minus the capacity of one disk.

Flex-RAID also allows you to choose JBOD formatting for your disks. JBOD, which is short for just a bunch of disks, refers to a set of hard disks that are not configured using RAID technology and that are treated individually by a computer. JBOD does not offer any data protection if a disk fails. However, some people choose to use JBOD because it maximizes

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