I just installed a 2tb harddisk in my Freenas 0.7.1
The system page of Freenas gives me the following info on this disk:
used - 0% of 1.8tb
total - 1.8tb
used - 4.0K
free - 1.6T
Do I understand it wrong when I think I just lost 400gb?
Yeah, pretty much. Welcome to the world of alternative accounting and filesystem overhead.
Hard drive manufacturers consider "TB" to mean "1,000,000,000,000" bytes of space, which is pretty much unlike the remainder of the compsci world, which operates on base2-derived numbers.
What that means is that when you have a "2TB" hard drive, it shows up to the OS as something smaller (like a WD EARS here -> 1907GB) and then the OS will put a filesystem on that, which typically also reserves some overhead space, of varying amounts. UFS used to set aside 10%. ZFS will set aside a varying amount that's confusing at best. Then there can be fun stuff like rounding to consider. And - while this isn't affecting your numbers yet - don't forget that filesystems store things in block-sized chunks, so storing a million 5-byte files uses up ~100x that much space.
In the end, it's best not to get too uptight over the size of hard drives. If you want to be able to *store* 2TB of data, best get a 3TB drive. Your 2TB drive can probably reasonably store 1.5TB of data. Otherwise, you'll get all Father-of-the-Bride hot-dog bun rantish and lose your mind. ;-)
