There are 5 Datacrons located on Voss and all of them are available for both factions.
Datacron 1 - Republic and Empire
Codex Entry - Galactic History 77: A Return to the Unknown Regions
Coordinates: -29, 372
This Datacron is located in the central-southern area of Voss-Ka but you can't get to it from Voss-Ka. You'll have to take a taxi to Fort Kodentha (for Empire) or Ken-La Outpost (for Republic) and go to the south-east corner of the Old Paths area at -442, 405. There you will find a path that leads to a cave. Follow it and at -435, 184 you should begin to climb the rocks. Very soon you will get to the cave entrance (at approximately -383, 132). Cross the cave, move forward a bit after you exit it and you will be able to see the Datacron.
Datacron 2 - Republic and Empire
Codex Entry - Galactic History 73: The Battle of Malachor Five
Coordinates: -1948, -2228
The first thing you need to know is that for this Datacron you need to have the Trials quest line at the Shrine of Healing completed. The quest line starts with the quest named "Roadblock" for Republic players and "The Gormak Problem" for Empire players.
Go inside the Shrine of Healing in the central room where you will see the Datacron (like shown in the second image). In the northeastern corner of the room there is a green crystal. Right-click on it to meditate and then you will be able to access the Datacron.
Datacron 3 - Republic and Empire
Codex Entry - Galactic History 76: Revan is Remade
Coordinates: 654, 2050
Go to The Gormak Lands at about 467, 1947 where you will find a rocky path filled with mobs. Follow it and you will soon reach a clearing. The Datacron is located behind a large rock.
Datacron 4 - Republic and Empire
Codex Entry - Galactic History 74: Revan and Malak Fall
Coordinates: 514, 175
The Cunning Datacron is located in The Nightmare Lands in The Boneyard Heroic area. To get to this Datacron you will first need to loot a Shield Decoder from a corpse near a damaged walker (at 442, 205). At the right of the walker there is a concrete circle with a red force field in the middle. Use any of the terminals to disable the force field and the circle area which is actually an elevator, will lower you to the Datacron.
Datacron 5 - Republic and Empire
Codex Entry - Galactic History 75: The Jedi Civil War
Coordinates: 2143, -840
The fifth Datacron is also located in The Nightmare Lands but for this one you'll have to go to the northeastern corner of the area. In the middle of the lake, at 2000, 940, you will find a meditation tablet. After you use the tablet you will enter the spirit world. The Datacron will be in front of you in the center of the room. After you collect it, you can exit the spirit world by using the meditation tablet again.