2-Understanding RAID

Volume Set

A Volume Set is seen by the host system as a single logical device. It is organized in a RAID level with one or more physical disks. RAID level refers to the level of data performance and protection of a Volume Set. A Volume Set capacity can consume all or a portion of

the disk capacity available in a RAID

 

 

 

 

 

Set. Multiple Volume

Sets

can

exist

 

 

 

 

Free Space

on a group of disks

in a

RAID

Set.

 

 

 

 

 

 

 

 

Volume 1

Additional Volume Sets created in a

Data

Data

Data

Parity

 

specified RAID Set will reside on all

Data

Data

Parity

Parity Volume 2

the physical disks in

the

RAID

Set.

Disk 1

Disk 2

Disk 3

Disk 4

 

Thus each Volume Set on the RAID Set

 

A 4 Disk RAIDset may contain two volumes. Volume 1 can be

will have its data spread evenly across

assigned a RAID 5 level of operation while Volume 2 might be

all the disks in the RAID Set.

 

assigned a RAID 0+1 level of operation.

 

 

Volume Sets of different RAID levels may coexist on the same RAID Set.

The maximum addressable size of a single volume set is 2 Terabytes.

Up to eight volume sets can be created in a RAID set

Online Capacity Expansion

Online Capacity Expansion makes it possible to add one or more physical drives to a volume set, while the server is in operation, eliminating the need to store and restore after re-configuring the RAID set. When disks are added to a RAID set, unused capacity is added to the end of the RAID set. Data on the existing volume sets residing on that RAID set is redistributed evenly across all the disks. A contiguous block of unused capacity is made available on the RAID set. The unused capacity can create additional volume set. The expansion process is illustrated as following figure:

Before Expansion: Disk Array A, 600GB

 

After Disk Expansion: Disk Array A, 800GB

 

 

 

Free Space

 

 

 

 

Free Space

 

 

200GB

 

 

 

 

400GB

 

 

Vol 1 (200GB)

 

 

 

 

Vol 1 (200GB)

 

 

Vol 2 (200GB)

 

 

 

 

 

 

 

 

 

 

Vol 2 (200GB)

Disk 1

Disk 2

Disk 3

 

Disk 1

Disk 2

Disk 3

Disk 4

200GB

200GB

200GB

 

200GB

200GB

200GB

200GB

The RAIDBank4 controller redistributes the original volume set over the original and newly added disks, using the same fault- tolerance configuration. The unused capacity on the expanded RAID set can then be used to create additional volume sets, with a different fault tolerance setting if required.

Array Roaming

The RAIDbank4 stores configuration information both in NVRAM and on the disk drives, and can protect the configuration settings in the case of a disk drive or controller failure. Array roaming allows the administrator the ability to move a complete RAID set to another system without losing RAID configuration and data on that RAID set. Should the RAIDBank4 enclosure cease to function, the RAID set disk drives can be moved to another RAIDBank4, inserted in any order, and become instantly available.

RAIDBank4 Owner’s Manual

16

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MicroNet Technology RAIDBank4 manual Volume Set