====== Name node ======
see also [[Secondary name node]]
  * :!: MOST IMPORATANT FOR CLUSTER! 
  * in-memory location of every [[Data block]] in cluster / rack
  * Controlls DataNodes
  * FS Ops 
  * Block Mapping
  * Send cordinates to clients where to get the [[Data blocks]] and witch [[Data node]]
  * [[Name node]] retrives every __3 secounds__ heart-bit from [[Data node]]
  * If [[Name node]] not retrives from the [[Data node]] heart-bit more then __10 minutes__ [[Name node]] will consedure the [[Data node]] as a [[Dead node]] and the [[Name node]] start to replicate all [[Data blocks]] that has on a [[Dead node]] to other nodes  

===== Requriements =====
  * Should have LOT OF RAM, LOT OF MEM, LOT OF POWER

===== Structure =====
  * RAM
    * [[Edit log]]
    * [[fsImage]] 
  * FILE
    * [[fsImage]] 

When proccess of Reboot or [[Checkpoint]] the [[fsImage|RAM\fsImage]] marges with [[Edit log]] to [[fsImage|FILE\fsImage]] file that makes it to keep presistnece.