The volumes on your ReadyDATA can be divided into shares and logical unit numbers (LUNs), both of which are logical entities on one or more disks.
LUNs are SAN data sets that allow data transfer and storage over iSCSI and Fiber Channel devices. The ReadyDATA supports iSCSI devices only. Dashboard displays LUNs in the following way:
Fig. LUN Icon
Shares and LUNs enable you to organize data in a volume by type, group, user, department, and so on. Within one volume, you can create multiple shares and LUNs, each one with its own specific configuration.
Each LUN has a configuration that is independent of other LUNs that reside on the same volume. A LUN configuration includes settings such as logbias, compression, deduplication (referred to as dedupe), protection, file-sharing protocols, provisioning, LUN size, and access rights.
The configuration settings of a LUN are stored in the volume (that is, in the pool) in which the LUN resides. This design allows a LUN to be portable when a disk is moved from one array to another array. However, iSCSI settings are not moved when you migrate a LUN from one volume to another volume or when you move the disk or disks on which the volume with the LUN resides to another array. For information about how to configure the iSCSI settings, see the How do I configure LUN access through an iSCSI initiator on my ReadyDATA storage system?
You can specify whether a snapshot is created, and with what frequency it is created.
You can specify the size of a LUN in two ways:
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Thin. Even though you specify the size of a thin LUN when you create it, storage space is assigned on demand instead of up front. This method greatly improves the utilization rate of the LUN because storage space is assigned only as data is written to the LUN. However, the size of the LUN is reported as the total storage space that you specify when you create the LUN. As data is written to the LUN, the used storage space is displayed on the volume icon in purple.
A thin LUN lets you overallocate its size, that is, you can assign a LUN size that is larger than the size of the volume. You can then expand the volume as needed (if necessary, adding disks in the process) without expanding the size of the LUN, and therefore without disconnecting users. Make sure that you watch the volume capacity of the volume on which the overallocated LUN resides so you do not run out of storage space unexpectedly.
Note: NETGEAR recommends that you do not use an overallocated LUN for storage of critical data. Instead, use a thick LUN.
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Thick. All storage space that you specify when you create a thick LUN is also allocated up front, and the storage space is reserved on the volume. Snapshots, other LUNs, and shares on the volume cannot consume storage space that is reserved. The reserved storage space is displayed on the volume icon in orange. The size of the LUN is reported as the total storage space that you specify when you create the LUN. You cannot assign more storage space than the available nonreserved storage space on the volume. As data is written to the share, the used storage space is displayed on the volume icon in purple.
The following table explains the default settings of a LUN. You can change these settings when you create or change the LUN.
|
Item |
Default State |
|
Logbiasa |
Latency |
|
Compression |
Disabled |
|
Dedupe |
Disabled |
|
Protection |
Continuous |
|
Interval |
Daily |
|
Size |
No limitation |
|
Access |
Denied until you set permissions |
a. You can change the logbias only when you change the properties of a share.