RAID technology is becoming increasingly popular in storage environments because of the cost, performance and data integrity improvements it provides. By combining physical drives into a logical unit and presenting it as a single hard drive to the operating system, RAID allows you to store the same data in different places on multiple disks. Therefore I/O operations can overlap in a balanced way, improving performance and increasing protection.
For organisations considering a RAID
implementation, there are multiple factors that need to be looked at. We've compiled a few
resources on RAID technology to help storage professionals increase their RAID data protection,
decide where to implement this RAID technology and determine which RAID levels
effectively address their particular availability and reliability concerns, and more.
SearchStorage.co.UK RAID technology
Software
RAID versus hardware RAID: Pros and cons
RAID takes multiple disk drives and creates arrays that are resilient and highly available by
mirroring and striping data across them. It also builds in the means to recover from disk failure
using parity data. Processing is required to carry out those actions, and that can take place on
the host server's OS or in the storage array or controller. This is also called software RAID vs.
hardware RAID.
Recovering
from a two-drive failure in a RAID 10 configuration
A RAID 10 configuration comprises two or more mirrored pairs of drives. So in a RAID 10
configuration with four drives, data can be recovered if two of the drives fail. But recovering the
data depends on which drives in the RAID configuration fail.
How
to choose the right RAID configuration for a new storage-area network
A business intends to acquire a storage-area network (SAN) to move away from direct-attached
storage (DAS). Half of their data is in a business-critical SQL database and Microsoft Exchange
Server, while the other 50% consists of Microsoft Office documents. Martin Taylor helps them decide
which RAID configurations they should consider for their new SAN.
RAID
10 vs. RAID 1: Mirrored drives matter
While RAID 10 and RAID 1 are both mirroring technologies that utilise half of the available drives
for data, there's one crucial difference: the number of drives that can be used in a RAID group.
RAID 1 involves only two drives that are mirrored to provide resilience in the event of a single
disk failure. RAID 10 involves at least four drives, and creates a RAID 0 stripe set involving two
or more RAID 1 mirrors.
How
many disk drives do you need for RAID 10?
The minimum number of drives required for RAID 10 is four. RAID 10 is a combination of RAID 1 and
RAID 0, the first step of which is to create a number of RAID 1 volumes by mirroring two drives
together (RAID 1). The second step involves creating a stripe set with these mirrored pairs (RAID
0).
Which
RAID levels have the best price-to-performance comparison?
Configuring disk in RAID arrays brings a variety of benefits, most notably data protection and I/O
performance. But which RAID level wins in terms of price vs. performance? This story breaks down
RAID 0, RAID 1, RAID 5 and RAID 10 in terms of performance, protection and value.
Which
RAID level is best: the dual parity of RAID 6 or the mirrored data of RAID 10?
Many storage managers have a hard time deciding which RAID level will provide the best availability
and reliability. Should they use the dual parity of RAID 6 or the mirrored data of RAID 10? RAID 6
provides more usable capacity and can always protect against two simultaneous disk failures, while
RAID 10 doesn't require special hardware and its rebuild times are faster. This story takes a
closer look at RAID 6 and RAID 10 to help you determine which RAID level is the best fit for your
storage environment.
How to
define RAID levels
Looking for a level-by-level comparison of RAID technology? This story digs into the basics of RAID
by discussing mirroring, striping and parity error checking, as well as how each of these concepts
applies to the various RAID levels.
Ask
the expert: What are the pros and cons of Raid 1 and Raid 5?
Are you curious about the benefits and drawbacks of RAID 1 and RAID 5? Alastair Roy, technical
consultant at GlassHouse Technologies (UK), discusses why RAID 1 has been the RAID technology of
choice for high-end applications and why RAID 5 provides increased capacity options.
Post-RAID
products
Disk systems and drives are growing in terms of capacity, which is starting to make the reliability
and performance mechanisms, including RAID, that have worked for smaller disks obsolete. In
response, vendors are taking new approaches to redundancy and data protection in disk arrays that
don't use traditional parity RAID and rebuild approaches. Find out what this means for the RAID
technology space.
RAID
changes its stripes, but not its value
While industry experts say the shape of RAID has evolved and is handled differently than when it
first appeared 20 years ago, the core concept of combining drives to protect data lives on
regardless of the methods used. This story takes a look at how the RAID space is evolving with
technologies like distributed RAID, global RAID and hybrid RAID, and how storage vendors like EMC
and IBM are starting to leverage distributed parity technologies.
Find more resources and information about RAID levels
- Examining RAID levels: RAID 0 through RAID 6 (Podcast)
- RAID tutorial: What's on the horizon for RAID?
- Software RAID versus hardware RAID: Pros and cons
- Do RAID levels still matter?
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This was first published in September 2009
