can I add a external USB 1tb drive or will it to be too slow over usb 2.0
Cutting a piece of this and resting your external drive(s) on it goes a long way to help with thatOther than the interface difference, there should be no difference in drive lifespan. IMO, the biggest problem with external drive is vibration. A good enclosure with proper vibration absorption goes a long way to prolong the life of a external drive.
I use single attached drives for simplicity, to not have the backups for multiple computers on one drive, but mainly because they spin down entirely when the computer is off/sleeping. The size I need (1TB) are also very cheap.An external drive just seems so old fashioned these days.
Unless you like to roll the dice you are only really getting 6TB because you will have to mirror to get any drive fault tolerance.a guy at work has this and claims its the greatest thing ever
http://www.tigerdirect.com/applications/searchtools/item-details.asp?EdpNo=9168237
I'm almost at this point now, where I'm about to build a 'real' htpc. but I can tell you that I ended up with 8external drives because every time I've run out of storage, it's pretty hard to justify spending 800bux to build a new computer(that will STILL need be to spend 100-150 on a new HDD) vs simply buying another external drive for 100-150bux.It's great everyone can run 1080p on their USB2 hooked up to their Amiga or whatever but let's be honest if you're starting from scratch today is that what you're really going to recommend?
If you built your HTPC, it's pretty easy to build yourself a fileserver. You just need a case big enough to hold a decent number of drives (six is usually good number), a motherboard with enough SATA ports, a Celeron processor, a 300W power supply and a small SSD to put your OS on.
If you want something small that'll hold up to 6 x 3.5" HDD and a SSD:
Fractal Design Node 304 or Lian-Li PC-Q25
ASUS H87I-PLUS
Celeron G1840
4GB RAM
120GB SSD (depending on O/S)
Seasonic 300W ATX power supply
There are many options for O/S from WHS2011 to Amahi to FreeNAS and more.
If you don't care about small, a microATX tower by Fractal Design and a ASUS or Gigabyte micro-ATX motherboard with the same RAM, CPU, etc. will work also.
If you don't want to DIY the Synology and QNAP suggestions are good ones.
There is such a beast... It's called a SAS expander. Albeit it connects to a SAS card, which really are not that expensive. A Dell 6gbps card that supports expanders can be had for $75. The expanders themselves are pretty cheap, atleast the 3gbps ones (no particular need for 6gbps expanders for media storage). You could get em for about $20.I wish you could take a PC case and buy a very dumb "motherboard" that all your sata drives will attach to, along with a low watt power supply. From there the board connects via USB 3.0 or esata out. A DIY external enclosure.