What are RAID controllers?
RAID controllers provide an interface between the system and the storage drive. The abbreviation RAID stands for “Redundant Array of Independent Discs”. RAID describes the use of several hard disks in a system in order to achieve the largest possible storage capacity, but also to be able to restore data as securely and easily as possible in the event of a failure by storing data on several hard disks in parallel.
The task of the RAID controller is to organize these individual hard discs in a logical network and thus create a drive. The controller coordinates the data accesses to the individual hard disks. Depending on the RAID level, these can be mirrored in order to save data multiple times, or simply arranged next to each other as hard drives in order to provide as much storage space as possible. Various combinations of storage and mirroring are also possible.
Finding the right RAID controller
Depending on the hardware you already have and your requirements, you will have different needs when it comes to disk array controllers. You can find an overview of the most important specifications here.
RAID levels
RAID controllers support different RAID levels, which determine how data is stored on the individual hard disks. Disk striping, disk mirroring and different combinations of these offer various options for data backup. Which of these is the right one depends on the planned application. The most commonly used levels are 0, 1, 5, 6 and 10.
- RAID 0 - Disk Striping: Data blocks are distributed between the individual hard disks. There is no redundancy, i.e. data is only stored once and is not mirrored.
- RAID 1 - Disk Mirroring: All data blocks are also stored on another hard disk when they are saved. An identical copy is created to prevent data loss in the event of a malfunction.
- RAID 10 (actually 1+0) - Disk Mirroring and Striping: The data is first mirrored on at least 4 hard disks and then distributed in blocks. They are fully protected and can be processed quickly.
- RAID 5 - Disk striping with parity: As with RAID 10, data blocks are stored here with redundancy. However, parity means that only around a third of the storage capacity is required to back up the stored data.
- RAID 6 - Disk striping with double parity: The same principle as RAID 5 is used here. The difference is that the parity information is stored on two drives and not just one, which further increases security.
In addition to the actual RAID levels, you can also use many RAID controllers as host bus adapters (HBA) or in JBOD mode (“Just a Bunch of Disks”). This means that either all or only selected hard disks are used as individual disks and are not regarded as part of the RAID array. Depending on the manufacturer and model, mixed forms are possible, or you may have to opt for either the RAID or HBA function.
Interfaces
For the connections of the plug-in cards, it is important which PCI ports are available on the mainboard in order to be able to integrate the controller into the system. Most RAID controllers are plugged in via a PCIe x8 connection. The other interfaces on the controller determine how and how many drives can be connected to the server. Most controllers have external or internal SAS / SATA ports, but some also support NVMe.
Data transfer rate
The data transfer rate also depends on the interface type used to connect the hard disks. The higher the transfer rate, the faster data can be stored and retrieved. Typical performance for servers is 6 to 12 Gbit/s, depending on whether SAS or SATA cables are used. With newer technologies such as NVMe, up to 32 Gbit/s can be achieved.
Cache
A cache increases the performance of the RAID controller by accelerating write operations, as data can be temporarily stored there. Typical sizes are currently 1GB, 2GB up to 8GB. BBU (Battery Backup Units) or BBM (Battery Backup Modules) can also be integrated so that data from the cache is not lost in the event of a power failure. These modules can bridge the gap for up to 72 hours and retain the data until the regular power supply is restored.
RAID controllers from various brands
Here in our store you will find hardware RAID controllers from all well-known brands, such as Broadcom, Adaptec, Dell, Fujitsu and more. LSI was bought up by Broadcom, but the brand name can still be found on many older models. Adaptec belongs to the Microsemi company, which is why this manufacturer's name can be found in some descriptions. The same chipsets are often used for various brands. This results in functionally identical RAID controllers that are branded differently. When making your choice, you should therefore focus primarily on the technical specifications. Most controllers are universally compatible.
New and refurbished server components from HaehnleinIT Inc.
The majority of our products are used and refurbished. This means you can purchase technology at a reasonable price, and older systems can also be upgraded and supplied with spare parts. Not only does this mean lower costs for you, you are also opting for a sustainable alternative, as the used components that are reused mean that fewer new ones need to be manufactured and waste is also reduced. Select items we offer new as well. Our inventory is constantly growing and in case you're looking for specific parts that we don't yet offer, we're happy to find them for you. Message us and we'll help you find the right solution for your data needs!
