RAID levels defined

RAID 0

Characteristics: Disk spreads data across two or more disk drives to improve I/O performance by performing parallel I/O. One/nth of the data is on each of the disk drives where "n" is the number of disks.

Application: Provides high performance for reads and writes. However, there is no data redundancy. RAID 0 by itself should only be used for applications that can tolerate loss of access to data and data that can reproduced from other sources.

RAID 1

Characteristics: Disk mirroring provides data protection and enhanced read performance. RAID 1 mirrors data across two or more disks so that each disk is identical to each other. RAID 1 utilizes n+n protection doubling the number of devices needed.

Application: Read intensive OLTP and other transactional data for high performance and high availability. Other applications that can benefit from RAID 1 include email, operating systems, application files, and read and random intensive environments.

RAID 0+1

Characteristics: Stripe and mirroring of data to provide high performance (stripe) and availability (mirroring) using n+n number of devices. The loss of a disk drive does not impact performance or availability, as would be the case with RAID 0 while the disk stripe enhances performance.

Application: OLTP and I/O-intensive applications requiring high performance and availability. This includes transaction logs, journal files and database indices where the cost measurement is based on dollar per I/O, compared to dollar per unit of storage.

RAID 1+0 (RAID 10)

Characteristics: Similar to RAID 0+1, mirrors and stripes data to provide high performance (stripe) and availability (mirroring) using n+n number of devices. The differences is striping groups of disks together and then mirroring the stripe gr

To continue reading for free, register below or login

Requires Membership to View

To gain access to this and all member only content, please provide the following information (all fields required):

First Name:
Last Name:
Country: Select... Afghanistan Aland Islands Albania Algeria American Samoa Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory British Virgin Islands Brunei Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, Democratic Republic of Cook Islands Costa Rica Cote D'Ivoire Croatia Cuba Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia, The Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guam Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard and McDonald Islands Honduras Hong Kong Hungary Iceland India Indonesia Iran Iraq Ireland Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, North Korea, South Kuwait Kyrgyzstan Laos Latvia Lebanon Lesotho Liberia Libya Liechtenstein Lithuania Luxembourg Macau Macedonia Madagascar Malawi Malaysia Maldives Mali Malta Man, Isle of Marshall Islands Martinique Mauritania Mauritius Mayotte Mexico Micronesia Moldova Monaco Mongolia Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands Netherlands Antilles New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Northern Mariana Islands Norway Oman Pakistan Palau Palestine Panama Panama Canal Zone Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Puerto Rico Qatar Reunion Romania Russia Rwanda Saint Helena Saint Kitts and Nevis Saint Lucia Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia and Montenegro Seychelles Sierra Leone Singapore Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and South Sandwich Islands Spain Sri Lanka Sudan Suriname Svalbard Swaziland Sweden Switzerland Syria Taiwan Tajikistan Tanzania Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu U.S. Minor Outlying Islands Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Vatican City Venezuela Vietnam Virgin Islands Wallis and Futuna Islands Western Sahara Yemen Zambia Zimbabwe
Email Address:

I would like to receive a FREE subscription to Storage magazine online.
YesNo

Do you manage, evaluate, recommend, implement, support or purchase storage products, software or services?
YesNo

What is your average annual expenditure on storage including hardware, software and services?
Please select... $20 million + $10 to $19.9 million $5 to $9.9 million $1 to $4.9 million $500K to $999K $250K to $499K Less than $250K None

What is your role in purchasing?
Technical decision maker
Financial decision maker
Determine need
Evaluate products/services
Recommend and specify products/services
Implement products/services
None

By joining SearchStorage.com you agree to receive email updates from the TechTarget network of sites, including updates on new content, magazine or event notifications, new site launches and market research surveys. Please verify all information and selections above. You may unsubscribe at any time from one or more of the services you have selected by editing your profile or unsubscribing via email.

TechTarget cares about your privacy. Read our Privacy Policy

Application: OLTP and I/O-intensive applications requiring high performance and availability. This includes transaction logs, journal files and database indices where the cost measurement is based on dollar per I/O, compared to dollar per unit of storage.

RAID 3

Characteristics: Stripes with dedicated parity at the byte level and has a single dedicated disk drive that stores parity information using an n+1 approach in terms of the number of devices needed.

Application: This provides good performance for video imaging, geophysics, life sciences, or other sequential processing applications. RAID 3, however, is not well suited for applications requiring concurrent I/O operations from multiple users or I/O streams.

RAID 4

Characteristics: Same as RAID 3, but with block-level parity protection.

Application: Using read and write cache is well suited with file serving environments.

RAID 5

Characteristics: Disk striping and rotating parity protection using n+1 number of components provides good availability with good read performance for multiple concurrent users and I/O streams. Using a hot spare disk drive, data can be reconstructed (drive rebuild) to protect against a second failure once completed.

Application: Reduces the number of components required while providing good availability, good performance for reads, write performance is impacted if write cache not utilized. Good applications for RAID 5 include reference data, read intensive database tables, general file sharing and Web applications.

RAID 6

Characteristics: Disk striping with rotating parity using dual-parity drives intended to reduce data availability exposure during a disk drive rebuild, particularly when using larger capacity Fibre Channel and SATA disk drives. The issue with RAID 6, and any multidrive parity scheme, is performance overheard for parity calculations when writing data or rebuilding from a failed disk drive.

Application: In general, if you are looking for high-performance reads and writes, look at using smaller disk drives and avoiding RAID 6. If on the other hand you are looking to store large amounts of data where rebuilds can occur in the background, RAID 5 and RAID 6 can be a fit when properly configured to your application needs.

Check out the entire RAID Handbook.

About the author: Greg Schulz is founder and senior analyst with the IT infrastructure analyst and consulting firm StorageIO Group. Greg is also the author and illustrator of Resilient Storage Networks (Elsevier) and has contributed material to "Storage" magazine and other TechTarget venues.

Rate this Tip To rate tips, you must be a member of SearchStorage.com. Register now to start rating these tips. Log in if you are already a member. BROWSE BY TAG SAN management,   SAN (storage area network),   Primary Storage or Storage Hardware,   RAID,   Data storage hardware,   RAID technology,   Data Storage Basics,   SAN/NAS Update,   Advanced data storage components,   RAID,   Advanced Data Storage,   Disk Storage,   RAID,   RAID levels/explainers,   VIEW ALL TAGS Digg This!     StumbleUpon     Del.icio.us    RELATED CONTENT SAN management Storage Decisions Chicago 2009 Session Downloads Storage Decisions Session Downloads: Managing Storage Networks Track (Chicago 2009) Storage-area networks to become increasingly object based Data storage management in virtual server environments 10 Gb Ethernet bodes well for iSCSI Mellanox builds bridge to consolidation Best storage Products of the Year 2008 Wide stripe before you dive into SSD How your SAN will evolve New realities of green IT: STORAGE BIN 2.0 SAN management Research RAID Pivot3 and Seanodes increase performance, scalability of iSCSI storage products Fujitsu adds DX60 and DX80 midrange disk arrays to Eternus line Storage Decisions Chicago 2009 Session Downloads MAID technology remains underutilized The state of MAID in data centers MAID product roundup The evolution of RAID data protection RAID changes its stripes, but not its value Post-RAID products Faster disk drive rebuilds: Hot Spots RAID Research RAID technology Learn all about RAID storage How to choose the correct RAID level RAID 4 vs. RAID 5 RAID: It's alive Server-based RAID vs. controller-based RAID Cannot retrieve data from RAID How many disk drives do you need for RAID 10? RAID types and benefits explained RAID 10 and RAID 01: Same or different? Failed RAID drives need immediate attention RELATED GLOSSARY TERMS Terms from Whatis.com − the technology online dictionary Fast Guide to Storage Technologies  (WhatIs.com) fat provisioning  (SearchStorage.com) oversubscription  (SearchStorage.com) RAID  (SearchStorage.com) storage area management  (SearchStorage.com) storage area network  (SearchStorage.com) thin provisioning  (SearchStorage.com) unified storage  (SearchStorage.com) virtual provisioning  (SearchStorage.com) zoned-bit recording  (SearchStorage.com) RELATED RESOURCES 2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems Search Bitpipe.com for the latest white papers and business webcasts Whatis.com, the online computer dictionary DISCLAIMER: Our Tips Exchange is a forum for you to share technical advice and expertise with your peers and to learn from other enterprise IT professionals. TechTarget provides the infrastructure to facilitate this sharing of information. However, we cannot guarantee the accuracy or validity of the material submitted. You agree that your use of the Ask The Expert services and your reliance on any questions, answers, information or other materials received through this Web site is at your own risk.