What is RAID Storage?
RAID is short for Redundant Array of Independent Disks. As the name implies, the technology combines multiple physical disk drives into one or more logical units. People use it most for data redundancy or performance improvement, or both. For example, having RAID storage helps if you’d like to prevent data loss in a hard drive failure. It is also useful when you want to improve the disk performance while you have heavy disk usage. The implementation of RAID can either use a special controller (hardware RAID) or an operating system driver (software RAID).
Hardware RAID Storage and Software RAID Storage
Hardware RAID is a customized processing system. It uses different controllers or RAID cards to manage the RAID design independently from the OS. On the contrary, software RAID employs the processing power of the OS in which the RAID disks are. When it comes to the configuration options, hardware RAID has more options, including some hybrid ones. Those options may not be available with specific OSs. However, software RAID has its advantages as well. It also permits users to reconfigure arrays without being restricted by the hardware RAID controller. Cost-wise, the hardware RAID is typically expensive while the software RAID costs lower. After all, software RAID doesn’t require additional RAID controllers.
RAID Storage Levels
People use different data distribution layouts to achieve the required level of redundancy and performance. Each distribution way, referred to as RAID levels, has its name, such as RAID 0 or RAID 1. In this article, we will cover several popular RAID levels.
Before diving into RAID storage levels, we will first introduce some commonly used terms.
- Parity: a technique that checks whether data has been lost or written over during data transmission. In this method, a parity bit adds checksums to data, enabling the target device to determine whether the received data is correct. If it’s incorrect, the source device must resend the data.
- Mirroring: a storage technique that stores identical copies of data on two or more disks to create a redundant data set. With this method, if one of the drives fails, you can still get the data from the other disk or mirror disk.
- Striping: a method that involves writing data across multiple disks. Data is written across the drives in sequential order until it reaches the last disk drive. Then, it jumps back to the first drive and starts a second stripe before repeating.
RAID 0 - Performance
This level (requires minimum 2 disks) consists of stripping, but no mirroring and parity. That is to say, it offers no redundancy but excellent performance. With this RAID model, the more drives in the RAID 0 array, the faster speed it delivers. You could consider the maximum theoretical I/O rates of a RAID 0 array with four drives to be four times faster than a single drive. This is because you have multiple lanes instead of a one-lane for shipping the data back and forth simultaneously. However, if one drive fails, the data will be lost. Therefore, RAID 0 is ideal for non-critical storage of data that needs high read/write speed, such as on an image retouching or video edition station.
RAID 1 - Data Protection
A RAID 1 setup (requires minimum 2 disks) consists of data mirroring without parity or striping. This array stores all data on each disk for improved fault tolerance. In other words, the disk capacity is divided in half. One half is to store your data, and the other half is a duplicate copy of the data. This way, you can maintain the availability of your project even when one of the drives goes down. After all, another disk that contains exactly the same data is still running. However, this level doesn’t improve performance. RAID 1 is ideal for mission-critical storage, for instance, for accounting systems.
RAID 5 - Data Protection and Speed
A RAID 5 setup (requires minimum 3 disks) consists of block-level striping with distributed parity. Parity is a technique that checks whether data has been lost or written over during the data traveling. In practice, RAID devices use enhanced forms of parity checking, such as vertical and horizontal parity. RAID 5 uses one or more disk drives that contain parity information to enable it to rebuild data in case of a disk drive failure. RAID 5 is a good all-around system that combines efficient storage with excellent security and decent performance. As it requires more disks than the RAID 0 and RAID 1, the cost is a bit higher.
RAID 10 - High Reliability and Performance
RAID 10 is a combination of RAID 1 and 0. It requires at least four drives. RAID 10 or RAID 1+0 delivers very high I/O rates by striping RAID 1 (mirrored) segments. This RAID mode perfectly fits business-critical database management solutions that require maximum performance and fault tolerance. A system set to RAID 10 yields half the total capacity of all the drives in the array. Like RAID 5, the cost of RAID 10 is higher since it consists of at least four disks.
Now you should have a basic knowledge of RAID and be able to decide if you need RAID storage for your server. To sum up, RAID is an effective storage scheme for improving performance and increasing data redundancy. All RAID levels except RAID 0 offer protection from a single drive failure. However, RAID is not a substitute for backups. Backups will come in handy if someone accidentally deletes some critical data or if all drives fail simultaneously. Moreover, you can keep your backup offsite at your local to make your data even safe.
At DatabaseMart, we provide RAID 1 for some of our dedicated servers. If your project is mission-critical and needs to implement high availability, you can opt for the dedicated server with RAID redundancy.
