This tutorial explores the popular raid levels, RAID 0, RAID 1, RAID 5 & RAID 10, with diagrams and explanations.
What is RAID?
RAID – Redundant Array of Inexpensive (or Independent) Disks is a data storage solution that works by combining multiple disks connected to a computer into a single storage unit. Data is spread across the disks in different ways depending on whether data integrity, access speed, or both are priorities.
RAID can be implemented in software or hardware, and the Linux Operating systems support RAID out of the box (as does pretty much every other operating system).
The different ways in which data is spread out across the drives in a RAID configuration is called the RAID level. Read on for an explanation of what they are and what they’re useful for.
Raid Levels
Below we’ll explain how data is distributed in RAID, with diagrams. The labels in the diagrams are as follows:
- DISK [number] refers to a physical hard disk device
- A -> F are blocks of data – files in the RAID storage.
- P[number] is parity – this is error-checking information regarding the data being so that the integrity of files can be checked and data can be reconstructed in the case of a fault with a drive
RAID 0 – Striped
- At least 2 physical disks are required.
- Best for performance as you can read from two disks at the same time, doubling the speed!
- The more disks, the more performance!
- The more disks, the more storage space!
- However, there is no redundancy – if data is lost, it’s lost.
- The more disks, the more chance of a failure
- Don’t store anything important in RAID 0
RAID 1 – Mirrored
- At least 2 physical disks are required.
- A copy of your files on each drive – great for storing important files
- Good read speeds! As your computer has two disks to read from
- However, write speed isn’t so hot.
- Adding more disks doesn’t increase storage space, just the number of copies of your data.
- Store your important files in RAID 1 if performance isn’t a consideration
RAID 5 – Striped with parity
- At least 3 physical disks are required.
- Uses parity – each drive has parity data for the other drives.
- Good read performance due to multiple disks being read simultaneously
- Parity allows for the recovery and repair of corrupted data.
- If one drive fails, the others can make up for it using their parity data, giving you time to replace the broken drive.
- As with RAID 1, write speed isn’t great.
- Store your important files in RAID 5 if you want more pooled storage space but are also concerned about losing data
RAID 10 – (RAID 1+0)
- It’s RAID 1 + 0, NOT RAID “ten”
- It combines RAID 0 and RAID 1
- Requires at least 4 disks
- Great data security as there are multiple copies of your data
- …AND great performance as there are multiple copies to read from
- The best option for reliability and performance, but overkill for most users!
