A hydrodynamic bearing for an X-ray tube with a rotatable anode, comprising: - a rotatable shaft for supporting the rotatable anode; - a supporting bushing arranged to seal a length of the shaft; and - a bearing arrangement provided between the shaft and the supporting bushing, comprising a primary bearing mechanism and a secondary bearing mechanism; wherein the shaft is rotatably supported by the bearing arrangement in relation to the bushing; wherein the primary bearing mechanism comprises a plurality of grooves in a surface of the supporting bushing and/or the shaft, and a lubrication material contained within a sealed space between the rotatable shaft and the supporting bushing; wherein the grooves are operable to interact with the lubrication material; and wherein the primary bearing mechanism supports the rotatable shaft during a steady operating phase of the rotatable anode; wherein the secondary bearing mechanism comprises first bearing surface portions on the surface of the supporting bushing and second bearing surface portions on the rotatable shaft; wherein the first and second bearing surface portions are arranged opposite to each other; wherein the first and second bearing surface portions are provided as mutual contact surface portions; wherein the secondary bearing mechanism supports the rotatable shaft during a starting and a landing phase of the rotatable anode; and wherein the first and second bearing surface portions of the secondary bearing mechanism do not contact each other during the steady operating phase; wherein at least a part of the first and/or second bearing surface portions comprises a first or a first and a second bearing coating (18,24) having a lower coefficient of sliding friction and a higher wear resistance, compared to a basis material of the rotatable shaft and/or a basis material of the supporting bushing, the second coating different in composition to the first bearing coating; and wherein the first and/or second bearing coatings comprise a plurality of layers of materials, wherein at least two adjoined layers comprise different materials, wherein a first adjoined layer comprises tetrahedral coordinated amorphous carbon (t-aC) and a second adjoined layer comprises molybdenum disulphide (MoS 2). - a rotatable shaft for supporting the rotatable anode; - a supporting bushing arranged to seal a length of the shaft; and - a bearing arrangement provided between the shaft and the supporting bushing, comprising a primary bearing mechanism and a secondary bearing mechanism; wherein the shaft is rotatably supported by the bearing arrangement in relation to the bushing; wherein the primary bearing mechanism comprises a plurality of grooves in a surface of the supporting bushing and/or the shaft, and a lubrication material contained within a sealed space between the rotatable shaft and the supporting bushing; wherein the grooves are operable to interact with the lubrication material; and wherein the primary bearing mechanism supports the rotatable shaft during a steady operating phase of the rotatable anode; wherein the secondary bearing mechanism comprises first bearing surface portions on the surface of the supporting bushing and second bearing surface portions on the rotatable shaft; wherein the first and second bearing surface portions are arranged opposite to each other; wherein the first and second bearing surface portions are provided as mutual contact surface portions; wherein the secondary bearing mechanism supports the rotatable shaft during a starting and a landing phase of the rotatable anode; and wherein the first and second bearing surface portions of the secondary bearing mechanism do not contact each other during the steady operating phase; wherein at least a part of the first and/or second bearing surface portions comprises a first or a first and a second bearing coating (18,24) having a lower coefficient of sliding friction and a higher wear resistance, compared to a basis material of the rotatable shaft and/or a basis material of the supporting bushing, the second coating different in composition to the first bearing coating; and wherein the first and/or second bearing coatings comprise a plurality of layers of materials, wherein at least two adjoined layers comprise different materials, wherein a first adjoined layer comprises tetrahedral coordinated amorphous carbon (t-aC) and a second adjoined layer comprises molybdenum disulphide (MoS 2).