Is 15TB RAID5 with different controllers possible?

[AlExAkE]

I would like to build new htpc/server for myself, and I'm going to use Zotac H67ITX-C-E or Zotac Z68ITX-B-E motherboard with Lian Li PC-Q08B case. The case itself has space for 6 3.5" hard drives, 1 2.5" hdd, and 1 5.25" cd/dvd/blu-ray ROM. Therefor I would need 8 SATA ports available, 1 for DVD, 1 for 2.5" HDD with OS (Windows Home Sever 2011 or Windows 7 Ultimate), and 6 ports to put 3TB HDD on each, for 15TB RAID5 array. Both of those motherboard have 2 6Gbps SATA III ports, and and 2 or 4 3Gbps SATA II ports.

My question is, they probably use a different controllers for the different ports, but does that matter? Can I put a HDD on a SATA III port on Marvel controller and 1 HDD on SATA II port on Intel and make RAID with it? In addition, since the ports are not enough, I will buy RAID controller like this one: MODEL# IXBAY-PX237

PCI-E SATA x 5 & ESATA x1 SATA II Raid Card 6 Ports | eBay

Would that work? Or for RAID I need all the ports to be from 1 controller? Keep in mind, all of the controllers support RAID5. This controller here has only 5 internal, and 1 external port, so I cant use it alone to connect 6HDD on it. Can I use the 5 from here, and 1 from the motherboard, to connect 6 3TB hard drives, to create my 15TB RAID5 array? IF not, please give me some solution. Thanks

[wrswrsnz]

Re: Is 15TB RAID5 with different controllers possible?

It would be very unwise to create a 15TB raid5 array. The problem with most big SATA drives is the Unrecoverable Error Rate is only 10^14 bits or 12.5TB. On a 15TB array if a disk failed you have more than 100% chance of a second disk dropping offline before the array rebuilds - killing the array, data gone... Even 6 x 1TB giving a 5TB array using disks with 10^15 Unrecoverable error rate has a 4.65% chance of failure on the rebuild.

This also means you cannot read all the data off the 15TB array without an unrecoverable error occuring making a disk in the array drop out.

You need to use enterprise-class drives and methods to create big arrays where multiple drives are raid 5 or 6 to form a single LUN of only a few TB to a controller that then arrays these LUN's together into raid 5 or 6 arrays. It's expensive but guarantees good reliability. With this type of system each sub-array can tolerate 2 drive failures. By using raid 5 or 6 to provide redundancy for a LUN failure it means a whole array can dissapear and the data is still safe.

Then you have to consider how you will backup 15TB...

[wrswrsnz]

Re: Is 15TB RAID5 with different controllers possible?

However, to answer the actual question - yes it is possible to do what you want but you'll need to use software raid (something like Linux) on multiple plugin SATA cards or use a single hardware raid card with 6+ ports that can handle greater than 2TB arrays and an OS to support greater than 2TB. If you're using an OS based on MBR you won't be able to boot from the array.