RAID stands for Redundant Array of Inexpensive Disks. It is a method by which several disk drives are configured into a single logical disk drive. The purpose of using a RAID structure is to provide fault-tolerance, redundancy, lower latency, and higher bandwidth for read/write operations. There are six types of basic RAID structures available, RAID-0 to RAID-5. Other RAID configurations are combinations of these basic types. The fundamental technique behind the RAID structure is of data striping. In data striping, each disk's storage space is logically divided into segments that can be as small as one sector (512 bytes) or as large as several megabytes. These segments are then interleaved in different ways (depending upon the type of RAID structure being used). The effect of this interleaving is that the data is written to the disks in a round-robin fashion (instead of being written to one disk at a time), hence, greatly enhancing fault-tolerance of the system.
What is stripe set (RAID-0)?
Stripe set (RAID-0) stores data in stripes on two or more physical disks. Stripe set does not provide fault tolerance, but offers better performance as compared to mirror set and stripe set with parity. Stripe set uses a minimum of three and a maximum of thirty-two hard disk drives.
What is RAID-5 volume?
A RAID-5 volume is a fault-tolerant volume with data and parity striped intermittently across three or more physical disks. RAID-5 uses a minimum of three and a maximum of thirty-two hard disk drives. If a portion of a physical disk fails, you can re-create the data that was on the failed portion from the remaining data and parity.
RAID-5 provides data redundancy at the cost of only one additional disk for the volume, while mirrored volumes use another disk of the same disk size, as that of the original data. RAID-5 volumes have better read performance than mirrored volumes.
Operating systems.
What is FAT file system?
FAT or FAT 16 file system is used to store data on a disk. The FAT file system is better suited for drives or partitions less than 200MB.
What is cluster remapping?
Cluster remapping is a recovery technique employed by the NTFS file system. Whenever a Windows operating system employing an NTFS file system generates a bad-sector error, NTFS dynamically replaces the disk cluster containing the corrupt sector and allocates a new disk cluster to the corresponding data. If the error occurs during a read operation, NTFS returns a read error to the calling program and the corresponding data is lost, unless there was some fault tolerance method (e.g., RAID) in place. However, if the error occurs during a write operation, NTFS writes the data to a new disk cluster. Hence, no data is lost. NTFS records the address of the cluster containing the bad sector in its bad sector file. Hence, the bad sector is not reused.