# mismatched replication level message running "zpool add"



## mrjayviper (Sep 17, 2012)

I have a pool of 4x 1TB running RAIDZ1. This was created using FreeBSD 9-stable (or whatever is stable at the time).

I have a spare 2TB that I want to add to the pool. I searched the net and found that the command to do this is "zpool add pool_name device_name".

I've tried these 2 commands:

```
1. # zpool add mypool /dev/ada4
2. # zpool add mypool ada4
```

And in both instances, I got a message that goes like
---------------
invalid vdev specification
use '-f' to override the following errors:
mismatched replication level
--------------------

This is my first time running 
	
	



```
zpool add
```
 so I'm not really sure if adding the parameter -f is safe. I just don't want to lose my data.

So I guess my question is: How do I add my 2TB hard drive to the existing 4x 1TB pool safely?

Thanks


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## phoenix (Sep 17, 2012)

If you want to keep redundancy, you can't.

You cannot add drives to an existing raidz vdev.  You can only add new vdevs to the pool.

Your add command was trying to add a non-redundant, single-disk vdev to the pool.  The other vdev in the pool is a raidz1 vdev.  Thus, the warning about different types and sizes of vdevs.

If you want to add more space to a pool, you have two options:

replace each individual drive in the existing raidz1 vdev with larger drives, which will expand the total available space in the pool once the last drive is replaced; or
add another raidz1 vdev to the pool, using the same number of drives as the other vdev uses
Option 1 adds more space without changing performance too much.  Option 2 adds more space and should increase performance as reads/writes will be striped across the two vdevs (like a RAID0 array across two vdevs).


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## mrjayviper (Sep 17, 2012)

please close. Thanks.


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