RAID 1 vs 2 Backup Copies on 2 Independent Disks

What do you guys think? I am not good at math, especially possibility calculation. Here is what I am wondering.

Is RAID operation (any level) inherently less stable/reliable than operating independent disks?

If the above is true, then wouldn't it be better to make 2 sets of backup on 2 independent disks? 1) You end up using the same number of disks anyway 2) In a RAID 1 array, when one of the independent disks fails, you are under the pressure to replace it immediately. On the other hand, in the case of 2 independent disks, you'll have immediate access to the backup on the remaining disk.

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Is RAID operation (any level) inherently less stable/reliable than operating independent disks?

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There is more overhead with the RAID controller reading/writing to multiple drives. The more complex you make the system, the more chances for something to go wrong. RAID0 was made for speed at the expense of reliability. RAID1 is slower, but has redundant data. You can't just lump them all together.

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If the above is true, then wouldn't it be better to make 2 sets of backup on 2 independent disks?

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Do you mean a RAID1 array with 3 drives instead of 2? Even if that were possible, that would waste a lot of resources. You'd buy 3 drives to get the equivalent storage space of just 1. It would slow the system down since it has to write the same data to 3 drives.

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On the other hand, in the case of 2 independent disks, you'll have immediate access to the backup on the remaining disk.

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Or do you mean backups as in backup images like TrueImage? If that's the case, then you would incur downtime while restoring the image. You'd only have data up to the last backup, so you would lose some data.

RAID1 is for availability. If you absolutely must keep the server up 24/7, then you'd need RAID1 (or better). Assuming you enabled hotswap, you just replace the bad drive and rebuild the array.

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RAID0 was made for speed at the expense of reliability. RAID1 is slower, but has redundant data. You can't just lump them all together.

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Sorry, I didn't say it clearly. I am not talking about RAID 0 vs RAID 1. I know the difference between the 2. I am saying that b/c any level of RAID involves operation of multiple disks "together", and so, like you say,

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The more complex you make the system, the more chances for something to go wrong.

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it demands more of the system and thus easier for something to go wrong as compared to a system operating independent disks. Probably not a good analogy but it's like, bouncing one ball in one each hand is a lot easier that juggling multiple balls with 2 hands. So, from your answer, it seems that RAID is inherently less stable/reliable than independent disks. Correct?

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Do you mean a RAID1 array with 3 drives instead of 2?

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This I don't understand. RAID 1 requires a min. of only 2 disks not 3. And, yes, I am referring to a RAID 1 array with 2 disks.

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Or do you mean backups as in backup images like TrueImage?

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I mean data files backup, NOT making a disk image.

The thing is this. In a RAID 1 array, when 1 disk is dead, I must go buy a new drive to rebuild the array in order to access my backup data again. However, if I just backup the same set of data twice, one to each of the 2 independent disks, if and when one of the 2 disks breaks, I don't have to necessarily replace it with a new one b/c my backup data will still be available on the other disk. I want to discuss whether this is a good backup strategy or not. This question comes about b/c I am tryin to decide on getting a NAS w/ RAID 1 or just a couple of USB drives for backing up my data. Of course a NAS offers other goodies besides RAID, but I am not considering those benefits in this discussion, just the backing up part.

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RAID is inherently less stable/reliable than independent disks. Correct?

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In the broadest sense, any extra overhead could be considered a liability. For RAID1, you're adding complexity to ensure uptime. It's a trade-off.

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This I don't understand. RAID 1 requires a min. of only 2 disks not 3.

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I know RAID1 is only 2 drives. I was trying to understand what you were talking about.

Sounds like you want to synchronize data on multiple drives, but not use RAID. There still has to be some software or other mechanism that syncs the data. That is adding complexity, so it's possible something could get corrupted.

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I must go buy a new drive to rebuild the array in order to access my backup data again

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That's not necessarily true. You can run on 1 disk with a broken RAID1 array. That's the point of having the RAID1; no downtime. I've done it with servers before. The system will be slower, but still operational. I'm not so sure about that NAS device you are talking about, though, so you probably want to download the manual before you purchase.

Data written identically to multiple disks is a "mirrored set", which is RAID 1, "mirroring" (without parity or striping).

Using RAID 1 with a separate controller for each disk is sometimes called duplexing.

I copy important stuff to a networked pc's drive and also to an external drive... The external drive is stored on the far side of the building incase of fire. Just good old plain and simple.

I have 4 computers at home that I wanna replace them w/ new ones. This is costing quite a bit already. Thinking to add a NAS too but it will add another $500 or so to budget. Thinking just get a couple of 1TB drives and use the free Synback Free(excellent freeware) which I am already using and like very much.

If you are going to have one of the old computers left over, you might consider adding some drives and installing the original version of Windows Home Server on it. You could then automate the backups of the 4 new computers using that. That should only cost you about $100 plus the additional hard drives.

Normally, that would be a great idea ... thanks, didn't even think of it. But these computers are aging and not so reliable anymore ... reason to replace them, so I am relutant to use any of them as a server.