1. A method for use in reserving storage space in data storage systems, the method comprising: reserving a set of logical units (LUs) predefined as file based storage hardware specific LUs in a restricted access storage space of a block based storage system, wherein the file based storage hardware specific LUs are inaccessible by a user of the block based storage system, wherein a first subset of the file based storage hardware specific LUs is configured using a first Redundant Array of Independent or Inexpensive Disks (RAID) scheme and a second subset of the file based storage hardware specific LUs is configured using a second RAID scheme, wherein the restricted access storage space is accessed by a file based storage system upon addition of the file based storage system to the block based storage system, wherein the file based storage hardware specific LUs stores information required for initializing the file based storage system; and initializing the file based storage system using the information stored in the file based storage hardware specific LUs.