Lacie 5BIG NETWORK, 2BIG DUAL, 4BIG QUADRA, 2BIG QUADRA, 2BIG TRIPLE 2-DISK RAID User Manual

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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.

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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

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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LaCie RAID Technology White Paper

RAID 5

Disk 1 Disk 2 Disk 3 Disk 4

B3 C3 D3

C2 D2

A2 B2

B1 C1

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. Data is striped across all disks and a parity block (P) for each data block is written on the same stripe. If one physical disk fails, the data from the failed disk can be rebuilt onto a replacement disk. No data is lost in the case of a single disk failure, but if a second disk fails before data can be rebuilt to a replacement drive, all data in the array will be lost.

Applications

RAID 5 combines data safety with efﬁcient use of disk space. Disk failure does not result in a service interruption because data is read from parity blocks. RAID 5 is useful for archiving and for people who need performance and constant access to their data, like video editors.

RAID 0

RAID 1

RAID 3

RAID 3+Spare

RAID 5

RAID 5+Spare

RAID 6

RAID 0+1

RAID 10

LaCie Products with RAID 5

LaCie 4big quadra ✦

LaCie 5big network ✦

How RAID 5 Capacity Is Calculated

Each disk in a RAID 5system should have the same capacity.

Storage capacity in a RAID level 5 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 5 array with four drives each with a capacity of 1000GB, the total capacity of the array would be 3000GB:

C = (4-1)*1000

Concatenation

JBOD

RAID Selection

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RAID 5+Spare

Disk 1 Disk 2 Disk 3 Disk 4

Spare

Cp C2

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. When a failed disk is replaced, the replacement becomes the new hot spare. No data is lost in the case of a single disk failure, but if a second disk fails before the system can rebuild data to the hot spare, all data in the array will be lost.

Applications

The main advantage of RAID 5+Spare is that users can continue to access data even while the data is rebuilt to the spare drive. RAID 5+Spare has good data safety but disk space is limited by the presence of the hot spare which is not used until one of the other disks fails. 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.

RAID 0

RAID 1

RAID 3

RAID 3+Spare

RAID 5

RAID 5+Spare

RAID 6

RAID 0+1

RAID 10

LaCie Products with RAID 5+Spare

LaCie 4big quadra ✦

LaCie 5big network ✦

How RAID 5+Space Capacity Is

Calculated

Each disk in a RAID 5+Spare system should have the same capacity.

Storage capacity in a RAID 5+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 5+Spare array with four drives each with a capacity of 1000GB, the total capacity of the array would be 2000GB:

Concatenation

JBOD

RAID Selection

C = (4-2)*1000

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LaCie RAID Technology White Paper

RAID 6

Disk 1 Disk 2 Disk 3 Disk 4 Disk 5

C3 D3

B3 C3 D3

A1 B1 C1

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. This Raid mode can support up to two disk failures with no data loss. RAID 6 provides for faster rebuilding of data from a failed disk.

Applications

RAID 6 provides data reliability with the addition of efﬁcient rebuilding in the case of a failed drive. RAID 6 is therefore useful for people who need serious security with less of an emphasis on performance.

LaCie Products with RAID 6

LaCie 5big network ✦

RAID 0

RAID 1

RAID 3

RAID 3+Spare

RAID 5

RAID 5+Spare

RAID 6

RAID 0+1

RAID 10

How RAID 6 Capacity Is Calculated

Each disk in a RAID 6 system should have the same capacity.

Storage capacity in a RAID 6 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 6 array with ﬁve drives each with a capacity of 1000GB, the total capacity of the array would be 3000GB:

C = (5-2)*1000

Concatenation

JBOD

RAID Selection

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LaCie RAID Technology White Paper

RAID0 RAID0

RAID 0+1

A B

B2 C2 D2

C1 D1

B1 C1 D1

Disk 1 Disk 2 Disk 3 Disk 4

RAID1

NESTED RAID LEVELS

RAID 0+1

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. In the diagram, at right, array B is a mirror of array A.

Up to two disks can fail in a RAID 0+1 array without loss of data, as long as the failed disks are not part of different RAID 0 pairs. In reference to the diagram, disk 1 and disk 2 could fail and the data would be preserved on disks 3 and 4.

Applications

RAID 0+1 provides good speeds because of RAID 0 striping, but cuts the available capacity of a device in half (assume all disks in the array have the same capacity).

RAID 0

RAID 1

RAID 3

RAID 3+Spare

RAID 5

RAID 5+Spare

RAID 6

RAID 0+1

RAID 10

LaCie Products with RAID 0+1

Currently, no LaCie products ✦

How RAID 0+1 Capacity Is Calculated

Each disk in a RAID 0+1 system should have the same capacity.

Storage capacity in a RAID 0+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 0+1 array with four drives each with a capacity of 1000GB, the total capacity of the array would be 2000GB:

C = (4*1000)/2

Concatenation

JBOD

RAID Selection

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LaCie RAID Technology White Paper

RAID 1 RAID 1

RAID 0

A2 A4 A6 A8

RAID 10

A6 A8

A1 A3

A1 A3 A5 A7

Disk 1 Disk 2 Disk 3 Disk 4

RAID 10

RAID 10 (also called RAID 1+0) is another RAID level that combines the attributes of other levels, speciﬁcally RAID 1 and RAID 0. It is a “stripe of mirrored sets”, meaning that data is striped across two mirrored arrays. 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.

In a RAID 10 array, one disk from each mirrored pair can fail with no data loss. However, the working disk in an array with a failed disk becomes a weak point for the entire array. If the second disk in a mirrored pair fails, the entire array is lost.

Applications

RAID 10 provides good speeds because of RAID 0 striping, but cuts the available capacity of a device in half (assuming all disks in the array have the same capacity).

RAID 0

RAID 1

RAID 3

RAID 3+Spare

RAID 5

RAID 5+Spare

RAID 6

RAID 0+1

LaCie Products with RAID 10

LaCie 4big quadra ✦

LaCie 5big network ✦

How RAID 10 Capacity Is Calculated

Each disk in a RAID 10 system should have the same capacity.

Storage capacity in a RAID 10 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 10 array with four drives each with a capacity of 1000GB, the total capacity of the array would be 2000GB:

RAID 10

Concatenation

JBOD

RAID Selection

C = (4*1000)/2

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LaCie RAID Technology White Paper

Concatenation

B C D

F G H

J K L

M N O

Disk 1 Disk 2 Disk 3 Disk 4

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 measure of data safety. It is simply a method of combining two physical disks into one volume for greater overall capacity.

Concatenation allows full use of the capacity of all disks in the array and most data can survive a disk failure. Only data on the failed disk and data that is partially written on the failed disk and an operative disk is lost.

LaCie Products with Concatenation Mode

LaCie 2big network ✦

LaCie Ethernet Disk ✦

LaCie 2big quadra ✦

RAID 0

RAID 1

RAID 3

RAID 3+Spare

RAID 5

RAID 5+Spare

LaCie 4big quadra

✦

How Concatenation Capacity Is Calculated

Storage capacity in a concatenation 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

For example, in a concatenation array with four drives each with a capacity of 1000GB, the total capacity of the array would be 4000GB:

C = (4*1000)

RAID 6

RAID 0+1

RAID 10

Concatenation

JBOD

RAID Selection

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JBOD

B C D

E F

K O

L P

M N

Disk 1 Disk 2 Disk 3 Disk 4

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.

LaCie Products with JBOD Mode

Currently, no LaCie products ✦

How JBOD Capacity Is Calculated

The total capacity of a JBOD array is the sum of the capacities of each of its disks, or

C = n*d

where:

RAID 0

RAID 1

RAID 3

RAID 3+Spare

RAID 5

RAID 5+Spare

C = available capacity

n = number of disks

d = disk capacity

For example, in a JBOD array with four drives each with a capacity of 1000GB, the total capacity of the array would be 4000GB:

C = (4*1000)

RAID 6

RAID 0+1

RAID 10

Concatenation

JBOD

RAID Selection

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LaCie RAID Technology White Paper

RAID 0

RAID 1

RAID 3

RAID 3+Spare

RAID 5

RAID 5+Spare

RAID 6

RAID0

RAID1

RAID3

RAID3+Spare

RAID5

RAID5+Spare

RAID6

RAID0+1

LaCie 2big quadra

H H

LaCie 4big quadra

LaCie big disk quadra

H * H *

LaCie little big disk quadra

LaCie Ethernet Disk

H H

LaCie 2big network

LaCie 5big network

RAID 0+1

RAID 10

Concatenation

JBOD

RAID Selection

RAID10

Concatenation

JBOD

* Built-in

H H

H H H H

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ABOUT LACIE

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, network and RAID solutions, optical drives, displays, and accessories are created to enhance and expand your computing environment, no matter its platform or conﬁguration.

Featuring the exclusive styles of world-renowned designers such as Neil Poulton, Ora-Ïto, Karim Rashid and Sam Hecht, LaCie’s award-winning products look stunning and perform with unparalleled reliability and versatility. LaCie is a global leader in manufacturing top-of-the-line tools that are often ﬁrst-to-market, constantly raising the bar and re-establishing industry standards.

Please visit our website: www.lacie.com, for up-to-date product speciﬁcations—available in multiple languages for worldwide accessibility. Use it to purchase items online, contact our excellent technical support or locate the sales ofﬁce or reseller nearest you.

www.lacie.com

While reasonable efforts have been made in the preparation of this document to assure its accuracy, LaCie assumes no liability resulting from errors or omissions in this document, or from the use of the information contained herein.