AJA IO LA, Installation And Operation Manual, Page: 17 / 76

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Io LD and Io LA Installation and Operation Manual — System Requirements
About RAIDs
Redundant Array of Independent Disks, or RAID, is a group of hard drives that
appears to the host Power Mac as a single high-speed storage unit. RAID systems
enable you to increase storage capacity and get the performance, reliability, and data
protection needed for video production, but not possible from a single hard drive.
RAID drives inside the array operate simultaneously, increasing overall throughput.
RAID technology is comprised of these techniques (some or all):
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Striping data across multiple drives for storage performance (RAID 0).
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Mirroring for redundancy (RAID 1).
•
Parity for data protection (RAID 5 [plus others]).
Most RAID configurations, or RAID levels, combine these to provide a balance of
protection and performance.
Striping divides a logical drive into data blocks, or stripes, that are distributed across
an array of physical drives. Striping a set of disks improves storage performance
because each drive operates concurrently. However, striping alone, known as RAID
level 0, offers no data protection.
Mirroring involves writing identical copies of all data to a pair of physical drives. This
results in very high data reliability: If one drive fails, the data is still available on the
remaining disk drive. However, it also results in a storage efficiency of only 50 percent,
because two physical drives are required to achieve a single drive’s capacity. Mirroring
alone is known as RAID level 1.
Parity provides data protection without requiring complete duplication of the drive
contents. In the event of a drive failure, parity information can be used with data on
surviving drives to reconstruct the contents of a failed drive. Parity data can be stored
on a dedicated drive, as in RAID 3, or distributed across an array of drives, as in
RAID 5. Parity provides much greater storage efficiency than mirroring—up to 85
percent for a set of seven drives.
Software For Striping
AJA recommends the Disk Utility software provided by Apple with OS X for creating
and striping RAIDs, including 3rd-party, SCSI, and Xserve RAIDs. It is very easy to
use and has been tested to work well. The utility can be found in
Macintosh HD/
Applications/Utilities, where “Macintosh HD” is the name of the system drive.
Note: Journaling should be turned off on drives used for realtime video.