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Expanding RAIDZ

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russdyer

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Sep 28, 2011
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I am creating a FreeNAS box but first had a ZFS question. Right now, I have 3 HDD (2x2TB & 1x1TB) and want to create a ZFS array. Later down the line, I may want to add a fourth or fifth HDD, but according to older (2010) videos/articles, I would need to rebuild to array if I want to add additional HDDs to it.

Is this still true with the newest version of FreeNAS, which runs ZFS v15? Can I add additional drives down the line without rebuilding the array?

Or do I need to have 5 drives to start with if 5 drives is my intended goal?
 

ProtoSD

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You need to have the 5 drives to start. Take a look at the 'unofficial FAQ' in my signature. You can add drives later, but it's not like just adding them to your original pool. This hasn't changed with newer versions of ZFS as far as I'm aware. I think with version 30 it *might* be possible, but I think that's still in developement.

Also if you mix drive sizes like you describe above, your total space will be based on the size of your smallest drive, so in your case it would be like using 3 1TB drives.
 

russdyer

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Ok, here is my setup: I have 3x1TB and 2x2TB drives. Right now, I have 2x1TB currently full in my media center, and 2x2TB and 1x1TB currently in my soon-to-be FreeNAS box. Because the 2x1TB are currently full, I wanted to setup the FreeNAS box on the 2x2TB and then move the data over and then add the 3x1TB. I am a complete newbie to FreeNAS but can two pools be setup (1st pool for the 2x2TB and a 2nd pool for the 3x1TB) and then merged as one? By the way, I would eventually want to replace the 3x1TB with 3x2TB but I just don't have an extra $250 right now. Because those 2x1TB are currently full is the reason why I was wondering if more drives can be added down the line.

My goal would be to have a total of 5x2TB with RAIDZ2.

So for the final recap, can I create 1 pool for the 2x2TB (move the data) and then create a 3x1TB pool and then merge them? Then swap the 3x1TB for 3x2TB for additional space?
 

louisk

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The short answer is no, you can't do what you outlined.
If you create a volume, you can't merge it with another volume you've created.
If your end goal is 5x2T RAIDZ2, I would (for now) store my data on the 1T drives you have (currently 3, 2 of which are full, so you still have 1T of growth room), and save up and buy 3x 2T to add to your 2x 2T. Once you have all 5x 2T, I would create the RAIDZ2 volume.
 

ProtoSD

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I am a complete newbie to FreeNAS but can two pools be setup (1st pool for the 2x2TB and a 2nd pool for the 3x1TB) and then merged as one?

@louisk is correct, but for example if you created the first pool and had your data, and then added the 2nd pool with empty disks and named your 2nd pool the same as the first, it would expand your pool and stripe the data. However, this can be a little complicated as far as redundancy and replacing disks with larger ones later. It's better to do what @louisk suggested. I just thought I'd mention it because you almost had the idea right.
 

russdyer

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I don't have the cash right now for 3 drives, but I think I will order 2 drives. That would give me 4x2TB for 8GB. If I did RAIDZ2, would this give me 6GB usable? How much under RAIDZ1?

Thanks for all the help.
 

ProtoSD

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It works out to a little less than 6GB because each drive is closer to 1.8GB, so you end up with about 5.3GB with Z2, and a little more than 6 with Z1.

@freeflow is correct below, I got mixed up. I have the 5 x 2TB and the capacities I mentioned are what I have.
 

freeflow

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4x2TB in RaidZ2 will give 4TB usable space because two of the disks will be used for parity information.
 

russdyer

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Question here...I got my two additional drives and created a volume with 4x2TB under ZFS RAIDZ2 and after creating my volume, it says that I only have 3.6TiB. Shouldn't I be closer to 6TiB (or like protosd says 5.3GB)?

Did I do something wrong here? and how do I remove a volume to try again?
 

ProtoSD

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I was having a 'senior moment' when I said 5.3TB, that is what I get with my 5x 2TB disks. 2TB disks are more like 1.8TB, so I think 3.6TB sounds about right since you need to subtract your parity.
 

russdyer

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Sep 28, 2011
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crap, I was hoping to get more than that. i guess i will try RAIDZ instead of RAIDZ2. i don't see 2 drives going at the same time.
 

Durkatlon

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Aug 19, 2011
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RAIDZ2 means 2 drives go to parity, therefore usable space is (4-2)*2TB = 4TB.

EDIT: sorry didn't see proto already answered.
 
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