It is determined that a first data unit is to be written to a storage device and that the first data unit is associated with a first attribute. In response to determining that the first data unit is associated with the first attribute, a first identifier is selected from a first identifier space and the first identifier is associated with the first data unit. It is determined that a second data unit is to be written to the storage device and that the second data unit is associated with the second attribute. In response to determining that the second data unit is associated with the second attribute, a second identifier is selected from a second identifier space and the second identifier is associated with the second data unit.