RAID
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RAID TOC | |
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[edit] Overview
RAID - Redundant Array of Inexpensive/Independent Disks
[edit] About RAID
For an excellent overview of the various raid levels, see the AC&NC RAID Tutorial.
Ideally, all partitions in a RAID block should be the same size. Any difference in the drives makes it harder for the computer to manage the RAID. It is recommended that only one IDE drive be connected per each IDE channel because a dead drive can bring down the whole channel. Also IDE does not provide for overlapping "seek", so accesses to another drive on the same channel -- even when both drives work properly -- will be blocked until the first drive is done transferring making the array slow. If you set up your RAID with two IDE disks per channel, you basically double your risk for losing the availability of your array since most RAID configurations can only sustain the loss of a single disk. Most users prefer RAID 1 or RAID 5 as they are a good balance between speed and increased data safety against hardware failure. With RAID 0, your chances of losing data increase by a factor equal to the number of drives.
[edit] On RAID Articles
First and foremost, make sure you have followed the guidelines to properly naming your article, and be sure that the title is preceded by RAID/. Secondly, insert {{TOC/RAID}} to the first line of your article. Thirdly, if you add a link here, you must add a link to Template:TOC/RAID.
[edit] Hardware
This is the original RAID method that most often has the greatest benefits for a RAID setup. Hardware RAID acts independently of any operating system, though a driver is still required by the operating system for it to function properly along side the hardware RAID controller.
[edit] Firmware
This excerpt from Wikipedia describes firmware RAID:
Hardware RAID controllers are expensive. To fill this gap, cheap "RAID controllers" were introduced that do not contain a RAID controller chip, but simply a standard disk controller chip with special firmware and drivers. During early stage boot up the RAID is implemented by the firmware; when a protected-mode operating system kernel such as Linux or a modern version of Microsoft Windows is loaded the drivers take over.
These controllers are described by their manufacturers as RAID controllers, and it is rarely made clear to purchasers that the burden of RAID processing is borne by the host computer's central processing unit, not the RAID controller itself, thus introducing the aforementioned CPU overhead. Before their introduction, a "RAID controller" implied that the controller did the processing, and the new type has become known in technically knowledgeable circles as "fake RAID" even though the RAID itself is implemented correctly.
- NVRAID with dmraid: Covers the installation and use of NVRAID.
- RAID/Onboard: Covers the installation and use of RAID array capabilities include on the motherboard. This kind of setup will allow you to dual boot Windows.
[edit] Software
Software RAID is achieved by the operating system. In Gentoo's case, Linux is used to create logical drives that treat multiple physical drives as a single drive, i.e., you do not need any particular hardware in order to have a RAID array. Since this is operating system specific, it can not be used simultaneously by multiple differing operating systems.
