Requires a minimum of two disks has no overhead

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Requires a minimum of two disks Has no overhead because all disk space is available for storing data This is the fastest of all RAID types. However, it does not provide fault tolerance. RAID 1 (mirroring) A mirrored volume stores data to two duplicate disks simultaneously. If one disk fails, data is present on the other disk, and the system switches immediately from the failed disk to the functioning disk. Mirroring: Provides fault tolerance for a single disk failure Does not increase performance Requires two disks Has a 50% overhead. Data is written twice, meaning that half of the disk space is used to store the second copy of the data. Overhead is 1 / n where n is the price of the second disk. RAID 1 is the most expensive fault tolerant system. RAID 5 (striping with distributed parity) A RAID 5 volume combines disk striping across multiple disks with parity for data redundancy. Parity information is stored on each disk. If a single disk fails, its data can be recovered using the parity information stored on the remaining disks. RAID 5: Provides fault tolerance for a single disk failure. Provides an increase in performance for read operations. Write operations are slower with RAID 5 than with other RAID configurations because of the time required to compute and write the parity information. Requires a minimum of three disks. Has an overhead of one disk in the set for parity information: (1 / n - 1)
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o A set with 3 disks has 33% overhead. o A set with 4 disks has 25% overhead. o A set with 5 disks has 20% overhead. RAID 10 (stripe of mirrors) A RAID 10 volume stripes data across mirrored pairs and across multiple disks for data redundancy. If a single disk fails, its data can be recovered using the mirrored information stored on the remaining disks. If two disks in the same mirrored pair fail, all data will be lost because there is no redundancy in the striped sets. RAID 10: Provides fault tolerance for a single disk failure Provides redundancy and performance Is the best option for I/O-intensive applications like database, email, web servers, or any other system requiring high disk performance Uses 50% of the total raw capacity of the drives is due to mirroring Requires a minimum of four disks Be aware of the following facts about RAID: Some RAID controllers support combined levels of RAID. For example, RAID 0+1 is a striped array that is mirrored. Other combined configurations that might be supported include RAID 1+0 (also called RAID 10), RAID 5+0, and RAID 5+1. For all RAID configurations, the amount of disk space used on each disk must be of equal size. If disks in the array are of different sizes, the resulting volume will be limited to the smallest disk. Remaining space on other drives can be used in other RAID sets or as traditional storage.
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  • Spring '14
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