I'm VERY confused at the confusion. RAID 10 is one of the most commonly used RAID levels today, just about every controller I've worked with supports Nested Arrays. (NOTE: I did say Controller, I would not know what Fake RAID, or BIOS/Software on board RAID supports, since I like my 30 year record of never having lost any data). IMO, I'd use RAID-6 for a server, but I'd brake your budget recommending all flash drives MANY, MANY more smaller ones.
(or if you have the resources, forget a new server and consolidate with VMware)
To REALYY answer your question Capt, "If you RAID0 2 4TB HDDs, is it possible to RAID10 2 4TBs and 1 8TB drive as backup" I will assume you made a typo and are really asking what TechyInAZ pointed out. If I may first restate your question, I think you are asking this:
"If you RAID0 2 4TB HDDs, is it possible to RAID10 2 4TBs (by using two more 4TB drives as the mirrors) and then subsequently backup the resultant Virtual 8TB RAID-0 array with one 8TB drive?" Is that more accurate? If not, ignore my answers, I will join the ranks of the confused, since you can't build a nested array (RAID-10) with less than 4 HDD's.
However, Capt Einstein, my guess is you already know that, (and type your question the wat you did to cut down on typing the obvious) since you were smart enough to know what very, very few people do know, how easy it us to back up a RAID-0 array with one single drive.
Of course it's possible, you can backup and restore ANY RAID level, from 0-60-100, but I would NOT use only 1 8TB drive, at the very least use three. (I am also assuming your backup drives are DAS, i.e., External).
What if your RAID 10 (or RAID 1 + 0 or 0 + 1) (Glorified RAID-1) Mirror becomes corrupted and you've been going along fine for 6 months and you don't catch the problem, and use only 1 8TB to conduct differential backups? You plop the 1 8TB in and now you have a corrupted server and a corrupted backup.
It's not that you can't do it, if you must, make certain to have one drive that is NOT part of the daily differential backups, i.e., it's Clean and can restore your mirror, if you need to completely wipe it out, worst case.
That's exactly how I run my workstation, not with 4TB drives, but with 8 Enterprise OCZ 400GB Enterprise SSD's implemented with an LSI-MegaRAID (ROC) Controller. RAID-0, I'm fond of very high speed storage, but again, it's my workstation, not one of our servers and now you know why. While RAID-10 is used a lot, I prefer RAID-6. However, RAID-10 comes right back into the picture, but only with what you said you do not want to use and that is a NAS/SAN (Hybrid is best).
Why not a NAS? You eliminate the issue of corruption, by stacking up a bunch of Point in Time Snaps, you can use Deduplication for regular backup and most decent NAS arrays (OK, I'm bias to EMC for obvious reasons) are one of the best investments a business can make.
If it's a cost issue, OK, but you need to consider cost when building a Server. You're obviously not building a Workstation, not with 2 4TB at RAID-0. If you were, you would not be concerned about adding a RAID-10 Mirror, since you already know you caan backup the 2 4TB drives as RAID-0 with 1 8TB Drive.
BTW, an EMC VNXe with Xeon CPU's lists out <10K and I get nice margins.
So:
1. YES, you can easily accomplish what you are looking to, but you already know 1 single 8TB drive is not enough cover for corruption. For a fire or if the server blows up, as long as you take the 1 8TB home with you, you're all set, but you need at least three if you want to do this on the cheap.
2. Or, visit
http://tinyurl.com/pholftr and at least give the VNXe a read. EMC has the best margins, I'm not bashful about "discounts" and if you like at a later time, you can take it right to DRaaS (Disaster Recovery as a Service) we do that as well.
Or, use the 8TB, but not one, use 3, or you're asking for trouble. Good luck.
Dean
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