Lacie 5BIG NETWORK, 2BIG DUAL, 4BIG QUADRA, 2BIG QUADRA, 2BIG TRIPLE 2-DISK RAID User Manual
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 capacity, 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 solutions. 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.
LaCie RAID Technology White Paper
A1
B1
C1
D1
A2
B2
C2
D2
A3
B3
C3
D3
A4
B4
C4
D4
RAID 0
Disk 1 Disk 2 Disk 3 Disk 4
STANDARD RAID LEVELS
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.
If one physical disk in the array fails, the data of all disks becomes inaccessible because parts of the data have
been written to all disks.
Applications
RAID 0 is ideal for users who need maximum
speed and capacity. Video editors working with
very large files may use RAID 0 when editing multiple streams of video for optimal playback performance. A RAID 0 array is more suited for actively
working with files (editing video, for example) and
should not be used as a single storage backup
solution or on mission critical systems.
RAID 0
RAID 1
RAID 3
RAID 3+Spare
RAID 5
RAID 5+Spare
RAID 6
RAID 0+1
LaCie Products with RAID 0
LaCie 2big quadra ✦
LaCie 4big quadra ✦
LaCie big disk quadra (built-in) ✦
LaCie little big disk quadra (built-in) ✦
LaCie 5big network ✦
How RAID 0 Capacity Is Calculated
Each disk in a RAID 0 system should have the
same capacity.
Storage capacity in a RAID level 0 configuration
is calculated by multiplying the number of drives
by the disk capacity, or C = n*d, where:
C = available capacity
n = number of disks
d = disk capacity
RAID 10
Concatenation
JBOD
RAID Selection
For example, in a RAID 0 array with four drives
each with a capacity of 1000GB, the total capacity of the array would be 4000GB:
C = (4*1000)
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LaCie RAID Technology White Paper
RAID 1
A1
B1
C1
D1
E1
A1
B1
C1
D1
E1
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. If one physical disk fails, the data
is available immediately on the second disk. No data is lost if one disk fails.
Applications
RAID 1 provides maximum data safety in the
event of a single disk failure, but because data
is written twice, performance is reduced slightly when writing. RAID 1 is a good choice when
safety is more important than speed.
LaCie Products with RAID 1
LaCie 2big quadra ✦
RAID 0
RAID 1
RAID 3
RAID 3+Spare
RAID 5
RAID 5+Spare
RAID 6
LaCie 2big network ✦
How RAID 1 Capacity Is Calculated
Each disk in a RAID 1 system should have the
same capacity.
Storage capacity in a RAID level 1 configuration
is calculated by multiplying the number of drives
by the disk capacity and dividing by 2, or
C = n*d/2
where:
C = available capacity
n = number of disks
d = disk capacity
For example, in a RAID 1 array with four drives
each with a capacity of 1000GB, the total capacity of the array would be 2000GB:
C = (4*1000)/2
RAID 0+1
RAID 10
Concatenation
JBOD
RAID Selection
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LaCie RAID Technology White Paper
A1
A4
B1
B4
C1
C4
A2
A5
B2
B5
C2
C5
A3
A6
B3
B6
C3
C6
Ap(1-3)
Ap(4-6)
Bp(1-3)
Bp(4-6)
Cp(1-3)
Cp(4-6)
RAID 3
Disk 1 Disk 2 Disk 3 Disk 4
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. If a second disk fails before data can
be rebuilt to a replacement drive, all data in the array will be lost.
Applications
RAID 3 provides good data safety for environments where long, sequential files are being
read, such as video files. Disk failure does not
result in a service interruption because data is
read from parity blocks. RAID 3 is useful for
people who need performance and constant
access to their data, like video editors. RAID
3 is not recommended for intensive use with
nonsequential files because random read performance is hampered by the dedicated parity
disk.
LaCie Products with RAID 3
LaCie 4big quadra ✦
How RAID 3 Capacity Is Calculated
RAID 0
RAID 1
RAID 3
RAID 3+Spare
RAID 5
RAID 5+Spare
RAID 6
RAID 0+1
RAID 10
Concatenation
JBOD
RAID Selection
Each disk in a RAID 3 system should have the
same capacity.
Storage capacity in a RAID level 3 configuration is calculated by subtracting the number
of drives by one and multiplying by the disk
capacity, or
C = (n-1)*d
where:
C = available capacity
n = number of disks
d = disk capacity
For example, in a RAID 3 array with four drives
each with a capacity of 1000GB, the total capacity of the array would be 3000GB:
C = (4-1)*1000
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LaCie RAID Technology White Paper
RAID 3+ Spare
Disk 1 Disk 2 Disk 3 Disk 4
A1
A3
B1
B3
C1
C3
A2
A3
B2
B4
C2
C4
Ap(1-2)
Ap(3-4)
Bp(1-2)
Bp(3-4)
Cp(1-2)
Cp(3-4)
Spare
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.
Applications
In RAID 3+Spare disk failure does not require
immediate attention because the system rebuilds itself using the hot spare, but the failed
disk should be replaced as soon as possible.
LaCie Products with RAID 3+Space
LaCie 4big quadra ✦
RAID 0
RAID 1
RAID 3
RAID 3+Spare
RAID 5
RAID 5+Spare
RAID 6
How RAID 3+Space Capacity Is
Calculated
Each disk in a RAID 3+Spare system should
have the same capacity.
Storage capacity in a RAID 3+Spare configuration is calculated by subtracting the number
of drives by two and multiplying by the disk
capacity, or
C = (n-2)*d
where:
C = available capacity
n = number of disks
d = disk capacity
For example, in a RAID 3+Spare array with four
drives each with a capacity of 1000GB, the total capacity of the array would be 2000GB:
C = (4-2)*1000
RAID 0+1
RAID 10
Concatenation
JBOD
RAID Selection
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