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ladegro

Areca 1220 Shrinking Raid-1 array

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Hi all,

I'm new to the forum so bear with me if I'm breaking any ground rules. This looked like the right place for my question though....

My linux server is run with an Areca 1220 PCI-X raid card. All eight slots are taken, 4 drives form a raid-5 array (1TB each), 3 drives form a raid-1 array (250GB each) and one drive is pass-through (2TB).

The OS is run from the raid-1 array.

Now, I have an urgent storage need. My idea is that the raid-1 array can do with just two drives just fine. That would give me the option to plug in an extra 2TB drive I have laying around as passthrough.

When I pull the 3rd 250GB drive, the array becomes degraded as expected, but besides that, runs just fine.

However, I'd like the array-state to be set to normal / aka have the array be rebuilt over just two drives without data loss.

I've searched around, but can't find this question on any forums. I e-mailed Areca and they reply the following:

Dear Sir/Madam,

data layout between 3 drives array and 2 drives array are different.
for your case, if you create a new array with 2 drives only, data inside are inaccessible.
Best Regards,

But with raid-1, data is just duplicated over all drives right? So I'm not sure about this answer. I've read methods using the RESETCAPACITY command, but that doesn't seem to work?

Anyone with good ideas? Thanks in advance.

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How exactly is your RAID1 setup? I'm not aware of a three-drive mirror (but then I'm not familiar with the ARC-1220)-- are you a 2-disk mirror plus hotspare? (sounds like not, but I'm not sure...)

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How exactly is your RAID1 setup? I'm not aware of a three-drive mirror (but then I'm not familiar with the ARC-1220)-- are you a 2-disk mirror plus hotspare? (sounds like not, but I'm not sure...)

It's a Raid 1+0 with 3 member drives. I think it once started out using a hotspare but then I though that spare could just as well deliver some extra performance by actively using it. But now I'd be more pleased if I could use the slot for another drive than that little extra performance on the OS drive...

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Well generally speaking when working with drives in this type of scenario, the safest option is moving the data to another location, recreating your RAID group the way you need it, then moving data back. Any live modification can result in dataloss.

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