I been researched and have couple Raid data storage for personal use. Hope I can provide you the answers here, ........ I don't go for dirt-cheap solution, I go for speed with durability and let not says cheap ...it’s affordable. :) The reason I have huge storage is not only for photo but my non-compression DVD movie. I think I have about 350-400 DVD movies in storage. But My photo is somewhere 350-400GB, Before you start, I say the 'cheaper' solution for photo storage is to get 3x750GB, one on board for data editing, one sync to backup on 2nd station then one store remotely. Believe me, this is much much cheaper approach to do.
If you have to do Raid 5, you still need backup for the data then another remote backup. It cost money for ya small storage.
Anyway.....My workings station is Raid 0 for OS (no data), single large disk for data(used as temp location for fast editing). Then a separate server storage in Raid 5 for all my media and images. That server again has separate Raid 0 OS for speed, sounds risky? Don’t be, all my os drives are well imaged and hard copied, in case of failure, I will just slide the mirror drive in and up and running in 5 minutes, if not, I have the image rewrite and back to work in less than15 minutes. Then I will sync my photo images to 2nd raid server as well as to hdd and store in remote location, aka my work place.
Anyway, let looks at your questions... you miss the hdd controller.
True, most recent mobo come equipped with 4,6 even 8 onboard sata drives Capability and allow Raid 0,1,5,10 but i prefer separate raid controller card for durability and speed!!. You would appreciate how fast the pure hw raid compre to sw for browsing, reading and writing. They also give you more options for common Raid features like online capacity expansion(OCE), online raid level migration (ORLM).
What is OCE? OCE gives you option to add new disks to existing raid with system online. Said you have 4x500GB raid 5 now, effective 1.5TB in use in 8x raid cards.
It's near its end and you have 2 options, built another raid on the available 4 slots and lose one disks for Raid 5 parity property. Or... add new disks and expand he existing raid, you don't get to lose the storage efficiency here.
ORLM allows you to change existing type of Raid to new type on the fly. Those you can modify the storage system without interrupting the operations. Say for instance you have more than u need for raid 5 8x500GB, 4TB and you decided it's too much for you, you change your mind for safer bet, Raid 6. The ORLM gives you option for that flexibility
A stand-alone Raid controller can be software or hardware X-OR. For instance, full line of highpoint card is software, notice they said optimize XOR. Then there's dedicate hardware XOR controller card like Areca with onboard processor. These onboard card will use it own processor for XOR calculation those reduce the cpu Utilization; therefore, it's a lot faster when it comes to rebuild, initialization and normal usage such as read and writes. They usually come with pci-x 64 bits or pic-e. I use both hw-sw before and decided to keep the my last highpoint sw cards for reasons below.
I have powerful server board, Xeon emt64. Highpoint support have been very good, they even respond to me during weekend. They went all the way tested the card by building one similar to my system. I still using the first ever FX series from AMD. :) and my last card with highpoint has been flawless. It's 'cheap' and effective. Their card also offers single raid cross adapter meaning you can cross join single raid more than 2 cards. I'll be expanding my 8x250Gb with another card and add disk to expand the raid this weekend. If it's good, i am going for max 16hdd single Raid 5. Wish me luck...
You don't need a server (OS) for your application; XP pro would do just fine. To use those dedicated raid card, you do need a moboboard offering pci-x or pci-e. Some card is backward compatible with legacy pic-32 but doing so you reduce the bus bandwidth, so I would look for a good server board that offers pci-x or pci-e. May be desktop with pci-e x4 and more.
If I can start all over again with nowadays has to offer, I would go for Areca PCI-Express ARC-1220 sata II x8. It's hw XOR and they are the best raid card you can find. Newegg has them. Keep in mind, it's pic-e x8, you only can used it on x8 or x16 slots. Normal desktop mostly offers x16 for video cards, x1 for useless slots. Highpoint just came out with x1 raid card but it's only good for 4 drives. You can use the dual x16 slots and split into x8, but then you video card only use the x8 bandwidth. Anyway, The server board I want to upgrade is Intel SE7520BD2SATAD2 but it doesn’t support the latest Woodcrest xeon dualcore. Unless you looking to turn this into giant workstation say quad core Xeon 5000 series else, go for cheaper solution.
How about areca pairs with those?
1) Intel mobo SE7520BD2SATAD2, onboard video, pci-e x8,x4,x1, 1 pci-x 133 and 2 pci-x 100. You'll have plenty option for both pci-x and pci-e.
2) Go for pci-x, Tyan S2676 without scsi but with pic-e x16, pci-x 133 and 2x pci-x 100. That's one i have and they have one cheap now at newegg open box for $180. you can use x16 for video card.
Enclosure... the box, you gonna need a big case with good airflow. I use this
http://www.bigplasticfork.org/chaotic42/case2.html. Cheap and BIG. one side for mobo and one side for pure hdd. Then get use hdd rack for 3 hdd in 2x5.25" bay. Each bay has it own 12mm fan, enough and plenty for airflow. No bling bling, pure case with good air circulation. I can stick in 16 hdd in this case, what i make me think twice is the power. I don't like the built but like the separate compartments.
Next, hdd selection. The 750Gb is expensive, 500Gb is ok but best bang for the buck has to be the latest perpendicular recording 320GB 7200.10 from Seagate, $100 a piece, 8x320Gb give effective 2.240TB less redundant disk and effective 2.086 TB after formatted. Rumors has it it's only using 2 platters, less is better, meaning chances of platter failure is less. Hdd failure is all about luck.... as long you are well prepared for backup and recovery. Any brand of selection will do.
Hitachi 500 is 5 platters, Seagate 500 is 4, WD is 4, Maxtor 500 is 4, Seagate 750 is 188gb per platter, so it's 4 but I heard darn thing is heat generator but I won't mind 750Gb x 8 for raid 5 if I have the money...LOL
Have funs and good luck, hope that helps