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LaCie 4big Quadra White Paper
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LaCie 4big Quadra White Paper

LaCie 4big Quadra White Paper

Raid technology
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Download this manual See also: User Manual
As specialists in data storage, LaCie recognizes that almost all computer users will need a storage or backup solution and that
people use and store data in different ways. Depending on their requirements, some people may prioritize performance and ca-
pacity, whereas others may be more interested in security and speed. In order to meet the storage needs of a wide range of users,
LaCie's professional storage devices utilize RAID technology.
RAID (Redundant Array of Independents Disks) is a simple technology that improves the performance of external storage so-
lutions. RAID allows you to choose the best way to use your device to fit your needs. Simply put, RAID technology either divides or
duplicates the task of one hard disk between many (or as few as two) disks to either improve performance or create data redundancy
in case of a drive failure. You can decide how the device handles data by setting its RAID mode.
This document describes the different RAID levels used in LaCie professional storage devices, and the characteristics used by each
mode to optimize the speed, security or storage capacity of the hard drives in the RAID array.
Important:
No RAID configuration will protect data reliability from software or file system corruption. As a result, LaCie recommends that
regular backups should always be performed to protect data.
RAID Terms
To better understand how RAID works, first familiarize yourself with the terms below:
Striping
is the splitting of data between multiple drives. Striped RAID arrays generally aim to merge maximum capacity
✦
into one single volume.
Mirroring
is the copying of data to more than one disk. Mirrored RAID arrays typically allow the failure of at least one disk
✦
in the array without any data loss, depending on the RAID level of the array.
Fault Tolerance
allows a RAID array to continue working (i.e. the data stored in the array is still available to the user) in
✦
the event of a disk failure. Not all mirrored RAID arrays are user friendly. For instance, some RAID devices must be shut
down before a failed disk is replaced, whereas LaCie RAID devices feature "hot-swappaple" disk replacement that allows
the device to remain on, and the data accessible, while the failed disk is replaced.
RAID Technology White Paper

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Summary of Contents for LaCie 4big Quadra

  • Page 1 RAID Technology White Paper As specialists in data storage, LaCie recognizes that almost all computer users will need a storage or backup solution and that people use and store data in different ways. Depending on their requirements, some people may prioritize performance and ca- pacity, whereas others may be more interested in security and speed.
  • Page 2 RAID 0 RAID 0 (also called FAST mode in some LaCie devices), is the fastest RAID mode. Requiring at least 2 drives, RAID 0 stripes data onto each disk. The available capacities of each disk are added together so that one logical volume mounts on the computer.
  • Page 3 RAID 1 RAID 1 (also called SAFE mode in some LaCie devices) is a secure RAID mode that requires at least 2 drives and works with pairs of drives. One logical volume mounts on the computer and the combined available capacity of both drives is limited to the capacity of the lowest-capacity disk.
  • Page 4 LaCie RAID Technology White Paper RAID 3 RAID 3 uses byte-level striping with a dedicated parity disk (Disk 4 in the illustrations, right) so that one volume mounts on the computer. A RAID 3 array can tolerate a single disk failure without data loss. If one physical disk fails, the data from the failed disk can be rebuilt onto a replacement disk.
  • Page 5 LaCie RAID Technology White Paper RAID 3+Spare In RAID 3+Spare, one disk in the array is left empty. If a drive in the array fails, the data from the failed disk is automatically rebuilt to the empty or “spare” disk.
  • Page 6 LaCie RAID Technology White Paper RAID 5 RAID 5 combines the striping of RAID 0 with data redundancy in an array with a minimum of three disks. The difference between RAID 3 and RAID 5 is that a RAID 3 configuration will offer better performance at the expense of slightly less overall capacity.

  • Page 7: Raid 5+Spare

    LaCie RAID Technology White Paper RAID 5+Spare RAID 5+Spare, is a RAID 5 array in which one disk is used as spare to rebuild the system as soon as a disk fails. At least four disks are required. If one physical disk fails, the data remains available because it is read from the parity blocks. Data from a failed disk is rebuilt onto the hot spare disk.
  • Page 8 LaCie RAID Technology White Paper RAID 6 In RAID 6, data is striped across all disks (minimum of four) and a two parity blocks for each data block (p and q in the diagram at right) is written on the same stripe. If one physical disk fails, the data from the failed disk can be rebuilt onto a replacement disk.

  • Page 9: Nested Raid Levels

    RAID 0+1 is a secure RAID mode that is composed of a mirror of striped sets. RAID 0+1 arrays should have disks in multiples of four. For LaCie products with five disks, in a RAID 0+1 array, the fifth disk will either be a spare or will be unused.
  • Page 10 The Striping occurs between arrays and the mirroring occurs within the same array, which makes the rebuilding very fast. RAID 10 arrays should have disks in multiples of four. For LaCie products with five disks, in a RAID 10 array, the fifth disk will either be a spare or will be unused. See the diagram at right.

  • Page 11: Other Configurations

    LaCie RAID Technology White Paper OTHeR COnfIguRATIOnS Concatenation When disks are concatenated, their capacities are combined and data is written to the primary disk in the array until is it full and then to successive disks. Concatenation provides no performance advantage or added mea- sure of data safety.
  • Page 12 LaCie RAID Technology White Paper JBOD JBOD stands for Just a Bunch of Disks. Each disk in the array, whether part of separate devices or the same device, mounts on the computer as a separate disk. JBOD LaCie Products with JBOD Mode Currently, no LaCie products ✦...
  • Page 13 LaCie RAID Technology White Paper RAID0 RAID1 RAID 0 RAID3 RAID 1 RAID3+Spare RAID 3 RAID5 RAID 3+Spare RAID5+Spare RAID 5 RAID6 RAID 5+Spare RAID0+1 RAID 6 RAID10 RAID 0+1 Concatenation RAID 10 JBOD Concatenation JBOD * Built-in Page 13...
  • Page 14 A B O U T L A C I E Through a combination of cutting-edge engineering and a rich history of unique design aesthetics, LaCie has earned an excellent reputation for producing products that are the perfect synthesis of form and function. Our hard disks, net- work and RAID solutions, optical drives, displays, and accessories are created to enhance and expand your computing environment, no matter its platform or configuration.