Get exclusive deals delivered to your inbox!

Start saving today. »

 
RAID Builder (find your RAID solution)
1. 2. Show RAID options

RAID Concepts 101

Volume (logical) vs. Disk/Drive (physical)

When discussing data storage, it is important to understand the difference between logical and physical.

When someone says,
"I have a 160GB hard drive in my computer." They are referring to the physical disk/drive.

When that same person says,
"There are two drives that show up on my computer." They are referring to the logical disk/drive, which is referred to as a volume.

When a physical drive is split logically into different volumes, this is called partitioning.

When discussing RAID technology, it is important to be aware of the differences between the logical and physical storage references.

Firmware

Firmware is essentially a small piece of software that resides on a piece of hardware to provide core functionality to the device as well as interface it with software and other pieces of hardware.

Firmware provides a basic set of operating instructions for the hardware device such as a hard drive.

It helps to think of firmware as a very basic OS (operating system) for a specific piece of hardware.

Drivers

Drivers, like firmware, provide a link from hardware to software.

Drivers reside onthe host OS (Mac OS X, Windows XP, etc.) and give functionality to the hardware present.

For example, your digital camera may require special drivers to be installed on the OS in order for it to transfer photos.

RAID

RAID stands for "Redundant Array of Independent Disks".

Put simply, this is taking two or more drives and putting them together logically to form a single volume.

This is done for speed, large storage space, redundancy, or any combination of the three.

To accomplish those objectives, the data moving on and off a RAID array is distributed in different variations unique to each objective or combination of objectives.

  • Definitions:
  • Show   
  • Hide   

RAID 0 (Stripe)
Data is split into blocks over two or more drives at same time for high speed and large capacity.
Capacity
blue meter 4
Data Safety
orange meter 1
Performance
green meter 4
RAID 1 (Mirror)
Data is written at same time to two drives only for highest level of data safety and redundancy.
Capacity
blue meter 1
Data Safety
orange meter 4
Performance
green meter 14
RAID 10 (1+0)
Data is Striped (RAID 0) over two Mirrored sets (RAID 1) of drives for fast redundancy.
Capacity
blue meter 2
Data Safety
orange meter 4
Performance
green meter 2
RAID 5 (Stripe with Parity)
Data is Striped (RAID 0) while incorporating parity over three or more drives for the best combination of speed, capacity, and redundancy.
Capacity
blue meter 3
Data Safety
orange meter 3
Performance
green meter 3
JBOD
(Just a Bunch Of Disks/Drives)
Each disk shows up as an individual logical volume on the computer. A 4 bay unit populated with drives will have 4 logical drives show up on the computer.
Capacity
blue meter 4
Data Safety
orange meter 1.5
Performance
green meter 1
Span (N-RAID)
Combines capacity of two or more drives of varying size without any RAID data distribution scheme into one logical desktop volume.
Capacity
blue meter 4
Data Safety
orange meter 1.5
Performance
green meter 1