Looking for a somewhat reasonably priced SATA RAID controller card with 6, 8, or 10 ports and capable of doing raid6. Pre-owned/Used is fine. [Not sure if this is possible, but if two four-port cards can be seamlessly combined into a single raid6, that would be fine too.]
Has to support the SATA 3Gbit/s (Second Generation) drives. Compatible with FreeNAS or similar.
Prefer the card to work in a normal 32bit PCI slot; but PCI-e and PCI-x (64bit) cards are ok if cost is much lower.
Inexpensive and RAID6 just does not go together in the same phase unfortunately.
RAID6 are found only in hardware RAID solutions and they're not cheap unless bought 2nd hand (pulled from servers). RAID5E (RAID5 with hot spare) is the alternative of RAID6 if a cheap (relatively) card supporting it is found.
If you're not looking for insane speed (>400MB/s) from an array, a cheap 2nd hand SAS RAID card like the Dell PERC 5/i I got (~$130 incl. cable+BBU) off eBay will do, that supports RAID5E. PERC 6/i are around $200+, >400MB/s capable and support RAID6. They are PCIe 8x and can be used in non-Dell server/workstation.
Since you are going to use FreeNAS then formatting with ZFS as your file system and running RAID-Z (better than RAID5, but can't do expansion) will be a much superior option with the bonus being no extra cost involved.
Cheap host/driver based RAID5 (aka fake RAID) is like poison if data is of high importance. The chance of array corruption and unrecoverable data is commonly heard here. While server-class hardware RAID cards have very high reliability rate for obvious reasons, hence cost.
after much research, it looks like the SAS cards (SAS supports SATA) are the most inexpensive way to go for a used RAID6 card. Be careful buying "cheap" PERC cards, because they make RAID and non-RAID cards -- there is a non-RAID PERC 6/i (as well as other models).
Unfortunately, my list of 'must-haves' on a RAID card (in addition to RAID6 support) are OCE (online capacity expansion: start with X number of drives in RAID6 and just add more drives as your space requirements grow), Spin Down Idle Drives (I think this is called MAID) -- I don't want the drives spinning if no one is using them & I am ok to wait ~30seconds to access the RAID for the drives to spin up), 64-bit LBA (meaning I can have volumes larger than 2TB), and Linux (FreeNAS) support.
I've looked at products from Adaptec, Areca, Promise, LSI (PERC). Promise is definitely out, since none of their offerings can spin down idle drives.
Strangely enough once you are over 6 to 8 drives, there is very little price correlation between the number of drives the RAID card supports and the price. The price difference between 12drive support and 16drive is soemthing like ~$100, the same for between 16drives and 20 or 24 drives.
Remembering that RAID6 'wastes' two drives; 8 drive support is 6 usable, a 12drive card is 10 usable... If my crystal ball told me that there would eventually be reasonably priced 5TB SATA II drives, I'd have no problem going with fewer supported drives. I'm more inclined to believe that 1.5-2tb drives are going to be the max under sata ii, and that higher capacities will come under the (where the heck is it -- it should be here by now) next revision of SATA (5ghz)...
another possibility for me would be to FreeNAS RAID0 a pair of drives dedicated solely to backup; which would then make an 8drive raid card more doable (since backups dont need to be raided anyway).
If you are using this thread as a reference, there are a few other (potentially costly) things to consider:
(1.) ECC RAM. a RAM error will crash your machine, and non-ECC ram is a terrible idea for RAID boxes. The ECC Ram requirement prevents you from re-purposing an old desktop pc/motherboard as a RAID box. Since most RAID cards have a CPU (RoC=RAID on chip, also know as an XOR Engine), you can get away with a much older server motherboard. I am aiming at a Pentium4 at 1.2GHz or faster, with 1gb (or more) ECC RAM.
(2.) CHASSIS. A case with 8, 12, 16, or 24 hot swap SATA/SAS drives is going to take a large bite out of your budget -- Don't forget to factor it in. There is no cheap way out of this one -- I thought about buying a 4u or 5u server and buying the hot swap bays separately -- which turns out to be more expensive since decent hot swap bays are $35 or more each (x10 and thats $350 PLUS whatever you spend on a 4u case, plus shipping. Next I thought about getting a old ebay scsi raid chassis, removing the scsi hardware and adding sata. except for two problems, first, they'd no longer be hot swap bays, and second, all the knuckleheads selling scsi raid chassis sell them without hot swap bays. So the cheapest way to do this is to pray for a sale at newegg or wherever on sata raid chassis.