MGMT 1050 Lecture 26: MGMT 1050 Lecture 26 Notes
MGMT 1050 Lecture 26 Notes – Mirrored Array
Introduction
• The most common of these are RAID 0, RAID 1, and RAID 5.
• RAID 1 is a mirrored array as described above.
• RAID 1 provides protection by storing everything at least twice
• Offers a substantial performance gain, particularly under heavy data read usage.
• RAIDs 2, 3, and 4 are arrays that are striped in different ways.
• Each uses a separate disk for error checking.
• Since data on every disk must be checked, this can create a roadblock on the single disk
that is used for error checking.
• RAID 5 eases the roadblock by spreading the error-checking blocks over all of the disks.
• RAID 0 is not a true RAID, because it provides no redundancy and no inherent error
checking.
• Data is striped across all of the disks, primarily for fast access.
• However, the lack of redundancy means that a failure of any single disk block in the
array corrupts all of the data in the system.
• However, this shortcoming can be overcome with proper backup and with certain types
of journaling file systems, which we will discuss
• It is also possible to nest ‘AIDs.
• For example, we can use a pair of RAID 0 groups inside RAID 1 to achieve mirrored
redundancy.
• The combination is known as RAID 0+1.
• With or without the additional protection, RAID 0 is sometimes attractive as a low-cost
method of achieving high data transfer rates when they are required.
• A number of vendors provide RAID controller hardware.
• Particularly for large RAID 5 systems.
• RAID controller hardware, RAID processing takes place within the array controller.
• The array appears as a single large disk drive to the computer.
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