Most people protect the gold storage very well because gold is a precious metal in the game. It costs elixir to upgrade the gold storage. A level 11 gold storage can store 2.000.000 million gold. At townhall level 9 you can have 4 gold storages.

Gold Pass modifiers

Town Hall 14

Increased storage capacity of level 13 Gold Storage from 2,500,000 to 3,000,000. The same update increased the loot cap at TH12 from 450k to 500k.

With Gold Pass you can upgrade its capacity to the maximum of 25 Million Gold and Elixir, and 250k Dark Elixir. Without Gold Pass, Season Bank is limited to 5 Million Gold, 5 Million Elixir and 50k Dark Elixir.

The maximum possible amount of loot remains the same. The December 2013 update reworked the loot system; Town Halls 6 and higher had less percentage available to loot from Gold Storages, but conversely had an increased loot cap (previously all Town Hall levels made 20% of Gold available, up to a maximum of 198,000).

Upgrading your Gold Storage to a higher level than you require for storage purposes can potentially save Gold in a raid. As an attacker receives an amount of Gold proportional to the percentage of damage each hit causes, the higher health of the upgraded building results in less Gold per hit.

With the gold in your gold storage you can purchase and upgrade buildings in your village. When you upgrade a gold storage it still works. Attackers can steal 20% of the total gold stored in your gold storage. That is a maximum of 198k gold from the storages.