I took a look at the specifications page you linked to. You have several options available to you.
Both the mSATA ssd and the hard disk drive can be replaced with new ssd's.
The mSATA ssd can be replaced with a larger capacity mSATA ssd and used like a normal ssd while the hard disk drive can be replaced with a standard 2.5 inch SATA 3, 6Gb/s ssd. You will have to do a fresh clean install of the operating system, drivers, applications, and utilities. My inclination would be to use a new SATA 3 6Gb/s ssd as the primary drive. The mSATA drive could be used for secondary file storage.
I maintain a consumer ssd database listed in a sticky at the top of this forum section. Luckily it still includes an mSATA section with larger capacity drives. I've been thinking of deleting the mSATA section as there isn't much interest in those drives. Here is the link:http://www.johnnylucky.org/data-storage/ssd-database.html
Scroll all the way down to the very bottom of the database where you will find about 17 mSATA models listed. Follow the links to the technical reviews where you will find more information about the drives. The technical reviews are divided into two groups - English language reviews and reviews in many other languages. There are no advertisements, pop-ups, or other distractions. It is strictly a hobby.