Software RAID has three disadvantages: ① it takes up memory space; ② occupy CPU resources; Software RAID programs cannot make the disk partition on which the operating system is installed into RAID mode. Because the RAID program runs on top of the operating system, the RAID functionality cannot be implemented until the operating system is booted. In other words, if the operating system is corrupted, the RAID program will not run, and the data on the disk will become a bunch of useless stuff. Because the data on the RAID disk can only be recognized and read and write correctly by the program that implements the corresponding RAID algorithm. If there is no corresponding RAID program, the data on the physical disk is just a few fragments, and only the RAID program can combine these fragments. Fortunately, most of the current RAID program will store their own algorithm information on the disk, once the operating system has a problem, or the host hardware has a problem, you can connect these disks to other machines, and then install the same RAID software. After the RAID software has read the RAID information stored in a fixed area on the hard disk, it can continue to use it. Software RAID has so many shortcomings that people are constantly thinking about more methods to implement RAID. Since software has so many drawbacks, what about hardware? RAID card is a method to implement RAID function with independent hardware. To realize RAID function in hardware, we must find a physical hardware as a carrier, SCSI card or motherboard on the south bridge is undoubtedly the carrier. Extra chips have been added to SCSI cards to implement RAID functions. These chips are specially used to execute RAID algorithm, can be ASIC such as high cost and high speed computing chip, can also be general instruction CPU such as general code execution chip, code can be loaded from ROM directly to execute, can also be loaded into RAM before execution, so as to realize RAID function. A RAID card (SCSI card or IDE expansion card) is called a RAID card. Similarly, the RAID function can also be implemented on the south bridge chip of the motherboard. Because the chips in the south bridge cannot rely on the CPU to perform their functions, these chips rely entirely on the circuit logic to operate on their own, and although they are fast, they are less powerful than the plug-in RAID cards. From some motherboard advertising can be seen, such as the so-called "onboard" RAID chip is the guide bridge to realize the RAID function of the chip. In this way, the operating system does not need to make any changes, in addition to the RAID card driver does not need to install any additional software, you can directly identify the virtual disk has been generated by RAID processing. For software RAID, the operating system to the actual perception in the bottom or at least the physical disk, but for the hardware RAID, the operating system cannot perceive the underlying physical disk, only by the manufacturer to provide a RAID card management software to view your card is connected on a physical disk. Also, when configuring a RAID card, it cannot be done in the operating system, but must be done by entering the hardware (or by using the RAID card configuration tool in the operating system). General RAID card is in the boot self test, into its ROM configuration program to configure a variety of RAID functions. RAID cards overcome the shortcomings of software RAID, so that the operating system itself can be installed on top of the RAID virtual disk, which is not possible with software RAID. Later I will also discuss the relevant knowledge of raid card from multiple dimensions. If you have any questions about storage technology, welcome to consult and answer your questions wholeheartedly. With more than 10 years of professional experience, STOR Technology Limited can also let you experience the original high-performance products at the factory price, such as: megaraid 9460-16i, megaraid 9560-8i, sas 9300-16i and so on. Contact us now！

Today we are going to talk about RAID implementation and configuration in the operating system. Some people write programs directly on the host, running at the bottom of the operating system, the physical disk submitted from the host SCSI or IDE controller, using the idea of seven stars Beidou, virtual into various modes of virtual disk, and then submitted to the upper program interface, such as volume management program. These programs use a configuration tool that lets you choose which disks to combine and form which type of RAID. For example, if two IDE disks and four SCSI disks are installed on a machine, the IDE hard disk is connected directly to the IDE interface integrated with the motherboard, and the SCSI disk is connected to a PCI interface SCSI card. In the absence of RAID program to participate in the conditions, the system can identify six disks, and after the file system format, mount to a disk letter or directory, for the program to read and write. After installing the RAID program, the user through the configuration interface, the first two IDE disks made a RAID 0 system. If the original IDE disk is 80GB, then RAID 0 will become a 160GB "virtual" disk. Then the user makes a RAID5 system with 4 SCSI disks. If the original SCSI disk capacity is 73GB, the capacity of the virtual disk after making the 4 disks into RAID5 will be about 3 disks, that is, 216GB. Of course, because the RAID program needs to use part of the disk space to store some RAID information, the actual capacity will be smaller. After being processed by the RAID program, these six magnets eventually become two virtual disks. If you are on the Widows system, opening Disk Manager will only show you two hard drives, one with a capacity of 160GB (drive 1) and the other with a capacity of 219GB(drive 2). The disks can then be formatted, for example, to an NTFS filesystem. The formatter has no sense that more than one physical hard disk is writing data. For example, the formatter may at some point issue a command to write data from memory start address so and so to disk 1 (a RAID 0 virtual drive consisting of two IDE disks) at LBA start address 10000 and length 128. The RAID program will intercept this command and analyze it. Disk 1 is a RAID 0 system, so the data of 128 sectors starting from LBA10000 will be calculated by the RAID engine, and the logical LBA will be corresponding to the physical LBA of the physical disk, and the corresponding data will be written to the physical disk. Once written, the formatter receives a signal that the write was successful and moves on to the next IO. After this process, the upper layer is completely unaware of the details of the underlying physical disk. The same is true for other forms of RAID, but the algorithms are more complex. But even though the complex algorithm, after CPU operation, it is thousands of times faster than the disk read and write speed. Tips: To ensure performance, only the same type of disk can be used for the same disk group, although it can also be designed to IDE magnetic Disk and SCSI disk are combined to form a virtual disk, but it is not designed this way unless specifically required. If you have any technical questions about storage, please contact me. I will be happy to answer your questions and provide you with original and new high-performance raid cards such as megaraid 9540 8i. hba card: such as LSI 9500 16i , LSI 9500 16e. 3 years warranty with high quality factory price, provide maximum security for you.