Lun Concatenation - Fujitsu ETERNUS DX S5 Series Design Manual

2. Basic Functions
Optimization of Volume Configurations
LDE works in terms of RAID group units. If a target RAID group contains multiple volumes, all of the data in the
volumes is automatically redistributed when LDE is performed. Note that LDE cannot be performed if it causes
the number of data drives to be reduced in the RAID group.
In addition, LDE cannot be performed for RAID groups in which the following conditions apply.
• RAID groups that belong to TPPs or FTRPs
RAID groups that are registered as REC Disk Buffers
•
RAID groups that are registered as Extreme Cache Pools
•
• RAID groups in which volumes are not registered
RAID groups in which WSVs are registered
•
RAID groups that are configured with RAID5+0 or RAID6-FR
•
LDE may not be available when other functions are being used in the ETERNUS DX or the target RAID group.
For details on the functions that can be executed simultaneously and the number of simultaneous executions,
refer to "Combinations of Functions That Are Available for Simultaneous Executions" (page
Caution
• If drives of different capacities exist in a RAID group that is to be expanded while adding drives, the
smallest capacity becomes the standard for the RAID group after expansion, and all other drives are
regarded as having the same capacity as the smallest drive. In this case, the remaining drive space is
not used.
If drives of different rotational speeds exist in a RAID group, the access performance of the RAID group is
reduced by the slower drives.
• Since the data cannot be recovered after the failure of LDE, back up all the data of the volumes in the
target RAID group to another area before performing LDE.
• If configuring RAID groups with Advanced Format drives, the write performance may be reduced when
accessing volumes created in the relevant RAID group from an OS or an application that does not
support Advanced Format.

LUN Concatenation

LUN Concatenation is a function that is used to add new area to a volume and so expand the volume capacity
available to the server. This function enables the reuse of leftover free area in a RAID group and can be used to
solve capacity shortages.
Unused areas, which may be either part or all of a RAID group, are used to create new volumes that are then
added together (concatenated) to form a single large volume.
The capacity can be expanded during an operation.
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Design Guide