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I'm trying to build a 16TB RAID system on the ultra-cheap. I don't have any experience with RAID, and basically I just want low-cost, improved performance. So as far as I know, RAID 0 fits the bill. Fault tolerance would be nice but is not necessary.

I know it's unwise in general, but what are the technical problems I might run into if I simply buy 8 random 2TB SATA drives on ebay? These can be had for about $50 each. Is there any reason the models need to be the same, the rotation speed needs to be the same, the SATA interface needs to be the same, the cache needs to be the same, or anything else?

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Eight 2TB drives in a stripe could do this, but make sure you have up to data backups and that you can reformat and restore of a drive failure. A ten 2TB drive in RAID6 is probably a much better solution. –  Hennes Jan 27 '13 at 10:26

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The short answer is no - especially for software RAID configurations, they do not have to be the same in any way. They do not have to have the same speed, interface, cache size, or medium (magnetic disk/SSD). They dont even have to be the same size (in bytes). FYI, when putting drives of different size in a RAID, the controller will set the size of all the drives to the smallest one in the group.

However, if you are using a dedicated hardware RAID controller, where the drives connect directly to it, then yes, the interfaces would have to be the same. Beyond that, the other options arent a factor in creating a RAID.

Still, it is definitely best to use the same model drives in a RAID, or at least as similar as possible.

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I've heard the opposite - that its a good idea to use drives of the same size s[eed and capabilities but different brands and batches to ensure that they fail at different times. Might be worth looking into, there's got to be some paper on it somewhere ;p –  Journeyman Geek Jan 27 '13 at 6:05
    
Im not saying that isnt true, but Ive never heard that. I can understand the reason behind diversifying manufacturers and batches, however the odds of multiple, same model/batch drive disks failing at the exact same time (or even within in the same month) seems infinitesimal. Taking caution to the extreme reduces practicality. –  Keltari Jan 27 '13 at 6:23
    
@JourneymanGeek It depends on the capabilities of the software RAID implementation. Difference in size, cache, speed, etc. will cause unexpected problems if whatever is controlling the RAID reaches unexpected limits be they an end of a platter, a response time for writing or reading, a difference in timeouts, and more. Some implementations won't even create the volume in the first place if there are certain mismatches between drives. TL;DR Your mileage may vary. (But it's a bad idea unless you hate your data, time, and life) –  Wesley Jan 27 '13 at 7:02
    
Maybe this analogy will help: Consider a RAID 0 (stripe) with two drives to transporting goods by cars. Every time a package arrives you sent off one car. With two cars to the same destination you could ship packages twice as fast. The easiest way would be to round-robin it. One package in car A, the next in car. Now mix cars, one with a speed of 54kmph, one with 72kmph, but still using round-robin. It will work, but it will be sub-optimal. –  Hennes Jan 27 '13 at 10:24

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