1. A storage system comprising: a storage processor coupled to a host through a PCIe switch and a storage pool made of PCIe solid state disks (SSDs), the storage processor including: a central processing unit (CPU) subsystem; the PCIe switch coupled to the CPU subsystem; and a memory configured to save tables, the CPU subsystem operable to communicate with the host and the storage pool through the PCIe switch, the CPU subsystem being operable to: receive a command from the host to write data, identified by logical block addresses, to the storage pool, the data organized into logical unit number (LUN) logical block address (LBA) groups with each group size being no less than a predetermined granularity; in response to the command, determine a number of LUN LBA-groups being added; based on the number of LUN LBA-groups being added, identify free locations within the storage pool addressed by storage pool free LBA-groups, the free locations accommodating storage of added data associated with the LUN LBA-groups being added, the free locations being used to store at least a portion of the data in the storage pool, at the location therein identified by the storage pool free LBA-groups, and upon being identified, the storage pool free LBA-groups becoming storage pool LBA-groups; link the storage pool free LBA-groups to the LUN LBA-groups by updating a mapping table included in the tables to add the LUN LBA-groups by using the LUN LBA-groups as indices for the storage pool LBA-groups; and access the storage pool to write the data by using the storage pool LBA-groups, wherein a size of the mapping table is increased to accommodate additional LUNs.