Storage space distribution method and device

The embodiment of the invention provides a storage space allocation method and device, and the method comprises the steps: allocating a storage space with the minimum guaranteed capacity to a to-be-newly-built target LUN under the condition that the capacity allocation mode of the to-be-newly-built target LUN is a simplified mode; when the target LUN is not enough to store the data to be written in the use process, enlarging the storage space of the target LUN, the data to be written in can be stored in the target LUN, and the enlarged capacity does not exceed the maximum capacity; and under the condition that the capacity allocation mode of the target LUN is a thick configuration mode, if the minimum guaranteed capacity and the maximum capacity are the same and the minimum guaranteed capacity does not exceed the current available capacity of the storage system, allocating the storage space with the minimum guaranteed capacity or the maximum capacity to the target LUN. For the situation that the specific capa