Viewstate is stored on page it self in encoded form. You can't access the viewstate in client side in a direct manner. You need to know the encoding/decoding algorithms to fetch the valuable data from this viewstate in clientside code.
You can use hidden variable to store data that will be used only on that page. Hidden variables are accessible from client side and server side code.
You can use Cache or session to store datatable (large data). They will have good performance as compare to ViewState.
The Cache is always using the machine's memory, the Session uses what has been configured:
In a web farm the Session can be local (which works only if affinity is set), or remote (state server or database, or custom), but the cache is always local.
So, storing a DataTable in the cache will consume memory, but it will not use serialization.
PS: storing a DataSet instead of a DataTable will change almost nothing.
Refer Cache Implementation
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