mySQL- large database
Can MySQL handle such big size database and can full text search really work for me for such 
  big database


What is big?

SERIOUSLY.

Let's have a look at modern hardware. Databases typcially are large when they are larger than the available RAM.

100gb - hm.

128gb memory was not particularly large last year.

Get a decent modern XEON, put 256GB memory into it.

Just checking - supermicro.com, website has a "featured motherboard". "Supports up to 256 GB DDR3 ECC". Ok, 128gb won't be that expensive.

I have a 64gb database server here that is 5 years old. I have a desktop server that has 64gb memory (micro atx board). Last time I checked, lower mid range servers (two sockets) go to 512gb memory.

That means that by all accounts, 100gb is not large.