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Hard drive raid advice

Nape Dog

Established Member
Evening all.
I am using a mac mini and using the disk utility I have raided my hard drives.
At present I have the following:
3x1tb WD mybooks striped to give one drive. Holds approx 1.3tb of stuff

1x2tb WD mybook backing up the 3tb auto using carbon copy cloner.

I have decided to get another 1tb drive and relegate the 2tb to the subs bench until I actually need it.

So, using disk utility, what is the best way to set up my 4x1tb drives so that they are giving me max storage which is backed up.


Established Member
I have decided to get another 1tb drive and relegate the 2tb to the subs bench until I actually need it.

Where Did the 2tb come from in the above sentence?

RAID can never ever ever to be considered a backup on its own. I'd set it up as raid 5 (this way one drive can fail without data loss). You would still need to take a backup of your most valuable data though:)

Nape Dog

Established Member
I have 5 drives in all. 3 x 1tb and 1 x2tb. The 1x2tb holds a backup of everything on the 3x1tb drives. As these hold a total of 1.1tb at present I have more then enough space however I want to only use 4x1tb at preset hence why I have bought another. The 2tb drives will be shelved until I use all space up and I will then but another 2tb to work along side the existing one.

I thought that if I were to set up a mirror raid situation i could use all 1tbs as one big drive with approx 2tb of storage which is a back up of itself and then if a drive fails I can just replace the failed drive. Am I wrong?


Established Member
Nape, I find your story hard to follow (could be just me as I'm a non-native speaker).

IF you want your phyiscal 4(?) 1TB hard drives to form one big logical 4 TB hard drive then yes, that is possible. Do realise that the faillure of only 1 of those 4 drives will render your 4 hard drive raid array inoperable (= broken) and you could lose all data stored on the raid array. In other words, there is no redundancy.

But you seem to have taken this into account as you have a external hard drive you use for backups?

Am I right so far?

Some more information so you can decide what you want:

In your post you mention mirroring, which does involve redundancy.Raid 1 is most often associated with this. It includes 2 hard drives with identical information on them. If 1 of them fails, you can rebuild the raid array by replacing the broken hard drive with a new drive, identical (or larger) in size. If the second drive fails and the raid array has not been rebuilt yet, you lose all your data. So raid 1 (mirroring) protects against 1 hard drive faillure. As both drives contain the same info, 2 x 1 TB is effectively only 1 TB. Raid 1 needs 2 drives, no more no less.

Then we have raid 0, striping. It also needs 2 drives exactly. Here you can add up the capacity: 2 x 1 TB will effectively yield 2 TB. If 1 drive fails, you lose all of your data. Raid 0 therefore, does not have redundancy.

All other raid levels are more or less offsprings of the 2 I have explained above. As soon as you want to use more than 2 hard drives (which is what you want), both raid 0 and raid 1 are out of the question.

You may need to look at raid 0 +1 or 1 + 0, or the most popular one, raid 5. Also take a look at JBOD (which is NOT a raid level!).

I assumed you were looking for some redundancy, and I quote "what is the best way to set up my 4x1tb drives so that they are giving me max storage which is backed up. ". Therefore, I advised raid 5 as it will tolerate 1 drive faillure (this is called redundancy)

But if you meant a backup, in the true sense of the word, there is no raid level that can offer you this (unless perhaps if you back up a raid array to another raid array). A good backup is preferably stored somewhere safe and is performed regularly. Just as you feel save (what are the odds that 2 drives fail at the same time?) bam, 2 drives fail. Or worse, lightning strikes and all drives fail:). The latter just to give an example that raid is not a backup.
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