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Are you frustrated
by slow boot times of your OS or load times of your games? When you
transfer or copy files does your computer tell you to just come back
tomorrow? Ever since the PC was invited we've been cursed with the
slowest component in a computer, the hard drive. Even though hard drives
have become much bigger and faster, they are still very slow when
compared to the other hardware in a computer. Eventually, the hard drive
as we know it will have to completely change, but for now we have to
live with what is readily available.
Even though hard
drives are slowing our computer experience down, there are ways to speed
things up considerably. There are a couple easy solutions. The first is
to choose a good Serial ATA hard drive like the Seagate Barracuda
7200.10 SATA 3.0Gb/s and the second solution is to run a couple of these
drives in RAID.
Today we begin Part
1 of our RAID project by testing the onboard SATA RAID on one of the
most popular enthusiast motherboards out today, the EVGA 680i SLI. We
will start out by explaining some of the basics about RAID and then test
a set of Seagate hard drive in RAID.
What is RAID?
RAID stands for
Redundant Array of Inexpensive Disks or Redundant Array of Independent
Disks. Simply put, RAID is a data storage scheme that uses multiple hard
drives to replicate data among the drives. Depending on the
configuration of the RAID or "RAID Level", the benefits of running RAID
can be increased by data integrity, fault-tolerance, throughput or
capacity.
Years ago the use
of RAID had only been seen in expensive servers. In recent years RAID
technology has become inexpensive and readily available to the average
computer user. Now days it's hard to find a motherboard that doesn't
have some sort of RAID offering.
RAID Levels
There are many
types of RAID levels, but some of the more popular levels are RAID 0
(Striping), RAID 1 (Mirroring), RAID 0+1 (Striping & Mirroring), and
RAID 5 (Block and Parity Striping). Let's take a look at these RAID
Levels so we have a better understanding of what each type does.
Striping (RAID 0)
When a disk array is striped, the read and
write blocks of data are interleaved between the sectors of multiple
drives (see Figure 11). Performance is increased, since the workload is
balanced between drives (or "members") that form the array. Identical
drives are recommended for performance as well as data storage
efficiency.
The disk array’s data
capacity is equal to the number of drive members multiplied by the
smallest array member’s capacity. For example, one 100 GB and three 120
GB drives will form a 400 GB (4 x 100 GB) disk array instead of 460 GB.
The stripe block size value can be set logically from 16KB, 32KB, and
64KB. This selection will directly affect performance. Larger block
sizes are better for random disk access (like email, POS, or web
servers), while smaller sizes are better for sequential access.
Mirroring (RAID 1)
When a disk array is
mirrored, identical data is written to a pair of drives, while reads are
performed in parallel. The reads are performed using elevator seek and
load balancing techniques where the workload is distributed in the most
efficient manner. Whichever drive is not busy and is positioned closer
to the data will be accessed first. With RAID 1, if one drive fails or
has errors, the other mirrored drive continues to function. This is
called Fault Tolerance. Moreover, if a spare drive is present, the spare
drive will be used as the replacement drive and data will begin to be
mirrored to it from the remaining good drive.
Striping/Mirroring (RAID 0+1)
A combination of both
above array types. It can increase performance by reading and writing
data in parallel while protecting data with duplication. A minimum of
four drives needs to be installed. With a four-drive disk array, two
pairs of drives are striped. Each pair mirrors the data on the other
pair of striped drives. The data capacity is similar to a standard
Mirroring array with half of total capacity dedicated for redundancy.
Block And Parity Striping (RAID
5)
RAID 5 calculates
parity in order to achieve redundancy rather than writing a second copy
of the data, like RAID 1. Parity is distributed across the physical
drives along with the data blocks. In each case, the parity data is
stored on a different disk than its corresponding data block. RAID 5
makes efficient use of hard drives and is the most versatile RAID Level.
It works well for file, database, application and web servers.
JBOD / SPAN
Another popular
RAID Array is "Just a Bunch Of Disks" or JBOD. As the name states, it is
simply a bunch of disk drives concentrated together to make one large
logical drive.
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