Introduction to Dorado thin LUN and thick LUN


SmartThin provides a storage management mode that supports on-demand resource allocation. Instead of allocating all storage space in advance, it first allocates certain storage space and dynamically allocates storage resources based on users' requirements (also called thin LUNs). The other type of storage resources that correspond to thin LUNs is thick LUN. The storage system uses the thin provisioning technology to allocate a fixed storage capacity to a LUN based on the capacity specified for the LUN upon its creation. For details, see: Basic Storage Principles.
When using thin LUNs, set the capacity overload of LUNs to not less than 10% of the storage pool capacity.
When a host initially reads data from and writes data to a storage system, thick LUNs deliver better performance whereas thin LUNs boasts higher space utilization.

Other related questions:
Introduction to the Dorado LUN copy feature
LUN copy is a data copy technology that quickly transfers data within a device or between devices. Full LUN copy replicates all the data of a source LUN and requires service suspension.

LUN requirements for deduplication
When a thick LUN is created, the relationship between its physical and logical addresses has already been fixed. This does not meet deduplication requirements. For deduplication, you must modify the mapping relationship between the physical and logical addresses. In addition, deduplication requires space reclamation. The pointer of the thick LUN's logical address cannot be changed. Therefore, the space cannot be reclaimed.

Method used to reclaim thin LUN space
You can use the following methods to reclaim thin LUN space: 1. Manually set the space size to zero. In this method, use a command to set the space value of the released space on a host to zero and reclaim the space. During the operation, the thin LUN space is fully occupied. Before performing this operation, you must stop services on thin LUNs. 2. Enable a storage system to automatically reclaim the released space. If the operating system on a host support thin LUNs, the operating system can identify the released space and deliver a specified SCSI command to a storage system. Then, the storage system will reclaim the released space.

Whether the Dorado supports LUN copy
All Dorado series storage systems support the LUN copy feature.

Whether the Dorado series LUN copy feature requires licenses
LUN copy is an optional value-added feature that requires a license.

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