Sorry for the late response, well I looked into FreeNAS a bit more, looks like from the stand point of my storage needs it will be what I need but it wants at least 8 (recommended 16) GB of ram and well my current machine has just 8GB. Raidz1 looks interesting. UnRaid looks good because of it's ability to run a pool with random disks but it reduces performance. Currently I'm running 3 1 TB drives in raid 0, performance is good but no redundancy. I just have movies on it but I would like to make backups as well.
So the main idea is that I want to build a server/NAS for home usage. I plan on buying the HDD's but I have to think firstly which OS to choose because if I choose FreeNAS I can go with 4x 2 TB HDD and I have 1 drive failure plus I can add a ssd for cache. For UnRaid I'd still have to buy the 4 HDD's but I have to get another 4 TB drive for parity and ssd for cache. On the last I have the option to use Storage Service on my existing Server but I don't know if I can create a RAID 5 with ssd cache. From what I have heard, ZFS is better than RAID in terms of redundancy. So what do you recommend? P.S The current server is also used as a Plex Media Server, FTP server, DNS server and Hyper-V host. I also had a webserver running and I might re-enable it.