Board index Linux RAID

Moderator: chandranjoy

RAID - Introduction

Postby chandranjoy » Fri Dec 31, 2010 7:48 pm

What is RAID?
RAID, short for the "Redundant Array of Independent Disks", is a technology to combine several hard drives into a single storage unit.

While the hard drives (called "RAID members") are relatively small, slow, and unreliable, the resulting array can be large, fast, and reliable. However note that while standalone drives are miserable but cheap, the drive array is perfect but expensive.

There are different RAID implementations, called RAID levels achieving different goals at different costs. Please read RAID types reference for an overview of these implementations.


Hardware RAID VS Software RAID:
The RAID can be implemented either using a special controller (hardware RAID), or by an operating system driver (software RAID).

Entry-level hardware RAID (integrated into the motherboard or a cheap RAID card) is similar in performance to the software RAID. Consider entry-level RAID hardware if the operating system does not support software RAID. Most common examples are
Use fault-tolerant arrays (RAID1 or RAID5) in Windows XP or Vista.
Boot Windows from a RAID0 or RAID5 (this is not possible using software even in Windows Server editions).
Enterprise-level hardware RAID controllers are feature-rich but expensive. They have certain features not possible in software arrays and never implemented in low-cost controllers, like caching, hotswapping, and battery backup. Additionally, certain RAID levels, like RAID50 and RAID60 can only be created with high-end controllers.
Software RAID, implemented by the operating system driver, is the cheapest and fairly versatile option. Most modern operating systems have the software RAID capability
Windows uses Dynamic Disks (LDM) to implement RAID levels 0, 1, and 5. However, fault-tolerant RAID1 and RAID5 are only available in Windows Server editions.
Linux uses either the MD-RAID or LVM for a software RAID.
However, there are certain limitations of a software RAID.
It is not possible to boot an operating system from a software RAID0 or RAID5.
No hotswap is possible with software alone, without a hardware support. So, software RAIDs have no hotswap.

Different RAID Levels:
http://www.raid-calculator.com/raid-typ ... rence.aspx

To Calculate RAID config:
http://www.raid-calculator.com

Here you can start the studies about RAID:
http://acnc.com/04_01_00.html
:)
chandranjoy
Site Admin
 
Posts: 283
Joined: Fri Oct 23, 2009 11:19 pm

Return to RAID

Who is online

Users browsing this forum: No registered users and 0 guests


cron