RAID at a Glance

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RAID at a Glance
ReadyNAS Products

What is RAID?

What is the easiest way to get RAID?

NAS for Home and Small Business

ReadyNAS NV+
TM

ReadyNAS 1100
TM

The Ultra Efficient 1U NAS

RAID (Redundant Array of Independent Disks) arrays allow multiple individual hard disks to be combined to perform as if they were one larger disk. The effect is to spread and replicate the data across the multiple disks (redundancy). That, in turn, reduces the risk of losing data if one drive fails. In short, RAID combines the capacity of multiple, independent hard drives into one while providing protection against data loss.

Many Network Attached Storage (NAS) devices use RAID technology to provide a large amount of storage with a level of fault-tolerance through redundancy. Although RAID in the past was reserved for enterprise companies, gone are the days when RAID comes at a high cost and requires IT specialists to manage it. RAID is now available in affordable solutions made specifically for home office and small business.

Do RAIDs make data safe?

Depending on how they are configured, RAID arrays can provide a good level of data protection through redundancy. If a single disk fails in the array, all the data will remain intact and accessible, and you will be given time to buy a replacement drive. No single drive solution offers data redundancy, so when the drive fails, all data is lost. In that case, the only option is to find a firm that specializes in data recovery and there is no guarantee that all of the data will be recovered. Even if it is, it will end up costing far more than it would have if you had used a RAID array in the first place.

Quick Glossary
Striping: Mirroring: Redundancy: Read performance: Write performance: Parity Data: Parity Drive: The splitting of data evenly across two or more disks The creation of an exact copy of a set of data on two or more disks Duplication of data which provides fault-tolerance in case of disk failure The speed at which a file can be transferred from the disks on the NAS to a client computer The speed at which a file can be transferred from a client computer to the disks on the NAS Redundancy information stored to the disks and used to reconstruct the data after drive failure A drive in the RAID array dedicated to storing parity data

RAID Level
RAID 0

Function
• Data striping • No redundancy • Requires at least 2 drives • Disk mirroring, no striping • Read performance improved; either disk can be read at the same time • Write performance same as single disk • Uses bit-level data striping • Stores error checking and correcting info

Benefits
• Best performance but no fault-tolerance • Disks are dependent on one another for data integrity • Best performance • Best fault tolerance in a multi-user system • No capacity increase with 2nd drive

RAID 1

RAID 2

• Repairs and replaces corrupt data • No advantage over RAID 3 • Method not currently used • Best for single-user systems • Any I/O operation requires activity on all disks • Cannot service multiple requests simultaneously • Services multiple I/O read requests simultaneously • No I/O overlapping for write operations, requires update to parity drive • Offers no advantage over RAID-5 • Low cost of redundancy • Read and write operations can be overlapped (limitation in RAID-4) • Best balance of performance, protection and capacity

RAID 3

• Uses byte-level data striping • Dedicates a drive to parity information • Embedded error checking information to detect errors • Uses block-level data striping • Dedicates a drive to parity information • Can read records from any single drive • Requires at least 3 disks • Uses block-level striping with parity data distributed across all member disks • Stores parity data across disks, but not redundant data (although parity information can be used to reconstruct data) • Requires at least 3 disks • Proprietary expandable RAID from Infrant Technologies • Automates volume expansion • Manages RAID details for you

RAID 4

RAID 5

X-RAID™

• Can expand from 1 HDD to 4 HDD • Can replace disks for higher capacity • Equivalent to RAID 5 in performance, protection and capacity • Offers fast sequential read and write operations • Offers extremely high fault- and drive-failure tolerance • Write operations slower due to dual parity • Can protect against 2 HDD failure but is really only suitable for 8+ drive systems • Rare in market • Higher performance than RAID-1 • Much higher cost • Requires 2X the capacity for redundancy

RAID 6

• Block-level striping • Extends RAID-5 by adding a second parity block that is distributed across drives

RAID 10

Combination of RAID-0 and RAID-1 Two subtypes: • RAID-0+1, data is organized as stripes across multiple disks, then striped disk sets are mirrored • RAID-1+0, data is mirrored and the mirrors are striped

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©2007 NETGEAR, Inc. NETGEAR, the NETGEAR logo, Connect with Innovation, Everybody’s connecting, the Gear Guy logo, IntelliFi, ProSafe, RangeMax, ReadyNAS, Smart Wizard and X-RAID are trademarks or registered trademarks of NETGEAR, Inc. and its subsidiaries in the United States and/or other countries. Microsoft and Windows are trademarks or registered trademarks of Microsoft Corporation in the United States and/or other countries. Other brand and product names are trademarks or registered trademarks of their respective holders. Information is subject to change without notice. All rights reserved. Product is subject to a limited warranty and actual product performance may vary due to real world operating conditions.

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