External RAID

hypochondriac · 29 Jun 2008 at 12:51

I'm not too learned on computers, I know enough to get me by, but I wish I knew more.
My question is, is it possible to get multiple HDDs, put them into some sort of external box and set up into a RAID array? If so how would one go about doing that?

Also in a RAID1 array, it is my understanding that, if one of the drives (or some of the data) malfunctions a little the second drive makes up for it and there is no data loss. But, does the RAID software repair the data using the second drive or do you just pray the same data isn't lost or corrupted on the second drive.

Finally, a side query, is a RAID 3 setup (with a parity section on the redundant drive) inferior in data protection to a RAID 1 setup?

hypochondriac · 29 Jun 2008 at 17:50

rpstewart said:
Either with a RAID controller of some form in the external device (WD & Lacie used to do this to provide 1Tb externals based on 500Gb disks)

What would I need to make such an external device? a housing, the HDDs, the RAID controller, a PSU, anything else?

rpstewart said:
RAID1 is purely for hardware redundancy. If the data is corrupt on one it will be corrupt on the other. RAID1 is no substitute for a backup.

Corrupted wasn't the word I wanted to use. Say the data on one disk goes wrong, or decays, (I'm not too sure what happens what data goes wrong), the other disk will have the correct data, but will it notice the error and correct it, putting it back to normal? or will I have to cross my fingers and hope the mirror data doesn't suffer the same fate.

hypochondriac · 29 Jun 2008 at 18:08

rpstewart said:
You basically buy the unit complete and add your own disks.

Do you recommend any?

rpstewart said:
If a block becomes unreadable on one disk but not the other then the controller will likely mark the disk as bad and revert to single disk operation.

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So it's like a safety net, not a regenerative array.

hypochondriac · 29 Jun 2008 at 20:01

rpstewart said:
Haven't look at any of them in detail, I keep all my disks internally.

It's just most of the multiply drive caddys on the OCUK site are for slotting into cases, (bar the Drobo box things).

One last question, is it possible to split a HDD into 2 equal partitions then set up a RAID 1 array with them? or does the redundant disk in a normal RAID 1 setup normally fully break all together, rather than part of it. Therefore making RAID between partitions futile.