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Is 15TB RAID5 with different controllers possible?

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June 2, 2011 1:13:23 PM

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

http://cgi.ebay.com/PCI-E-SATA-x-5-ESATA-x1-SATA-II-Raid-Card-6-Ports-/400206170389?pt=LH_DefaultDomain_0&hash=item5d2e258915

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

More about : 15tb raid5 controllers

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a c 289 G Storage
June 2, 2011 2:01:52 PM

To build a RAID 5 volume, you do need all the drives to be on the same controller. The controller is doing the work.
One solution, of course, is to settle for 12 TB and use five drives.
Another is to buy a RAID controller, as you mention. But be very careful: there are two classes of card. One does its own parity processing and is expensive. The other unloads parity processing on your CPU and is cheaper, but puts a load on your CPU that can be significant. And it's slower. I don't know who makes that card that you linked to.
Here are the cards that Tom's used to get 3GB/sec (that's bytes, not bits): http://www.tomshardware.com/reviews/raid-array-ssd,2915... . But it will set you back $500. Typically, going over 5 drives puts you in a new price category.

If you will settle for five drives, one of our members with more experience in RAID likes this device, which RAIDs five drives and presents the results as a single drive on a single SATA II Port:
Edit: Here's the link to the external version; there is an internal version too : http://www.datoptic.com/esata-hardware-raid-controller....
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a b V Motherboard
a c 415 G Storage
June 2, 2011 4:35:30 PM

You should be aware that very large RAID-5 volumes are generally not a good idea. When a drive fails in a RAID-5 set, the RAID controller won't be able to successfully rebuild the set onto a replacement drive unless it can read EVERY bit from EVERY functioning drive.

The problem with this (aside from the fact that it can literally take days, during which another failure can blow you out of the water) is that a lot of disk drives have an unrecoverable read error rate specification of 1 error in every 10^14 bits read. A 10TB array has around 10^14 bits. That means if you loose a drive there's as much as even odds that you WON'T be able to recover from a failure and you'll LOOSE ALL YOUR DATA.

I personally see no point of using RAID-5 with those kinds of odds. You'd be better to consider a hardware RAID controller that supports RAID-6, which uses two parity disks and a more sophisticated parity algorithm to eliminate that vulnerability.

Either way you go, though, be aware that with such large volumes you're in for a very, very long wait to initialize and copy data to them because of their poor write performance.
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June 2, 2011 8:13:50 PM

Oh, so you recommend RAID6. I will look into it. I've never been aware of the large volume problem. How large would you say should be the limit for RAID5? 10 TB, 12TB? YES, i do want to go definitely for hardware raid, as I've been told is better for several reasons. if you have any suggestions for controller supporting 5 or 6 ports with RAID6, that wont break the bank, please inform me of it. Thanks
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June 12, 2011 1:46:05 AM

Best answer selected by AlExAkE.
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