[Storage problem:] Massive OSx occupation

It uses more space for caches, temp. files, etc. The 15Gs is the minimal size immediate after installation but before using.

How to Free Up Space on The Hard Drive

You can remove data from your Home folder except for the /Home/Library/ folder.

Visit The XLab FAQs and read the FAQ on freeing up space on your hard drive.

Also, see Freeing space on your Mac OS X startup disk.

Free up storage space on your Mac.

See Where did my Disk Space go?.

Be sure to Empty the Trash to recover the space.

Replace the drive with a larger one. Check out OWC for drives, tutorials, and toolkits.

Use OmniDiskSweeper or GrandPerspective to search your drive for large files and where they are located.

I warn you to keep in mind that the amount of space OS X can take up may decrease or expand depending on what you are doing. I have put it on a number of small disks. Although immediately after installation it only used about 15GB, as soon as I logged in that quickly went to 32GBs as it makes a vm file equal in size to the installed RAM. On your machine that gets you up to 19-20GBs. Log files will be accumulating data and you need to allow some free space for OS X of about 12GBs on your SSD bringing you up to 32GBs. The rest of the SSD is for adding third-party apps, your files, etc. You have a small SSD so you will need to monitor your storage lest you fill up the SSD to the point where you corrupt the drive and lose all your data. That means you need to get a backup drive and maintain regular backups.