Mismatched replication level running zpool add

[mrjayviper]

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 so i get more storage/free space. 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

 

[brutalizer]

Dont add 2TB disk to your zpool! You are about to do something stupid!

EDIT:
You have four disks in RAIDZ1, which is similar to a raid-5: one disk can die without problems. If two disks die, you loose all data.

A zpool consists of group of disks. Say a zpool can consist of two raidz1 groups of 5 disks in one group and 4 disks in another group. So in this case, each group can loose one disk without problems. If you loose two disks in the same group, you will loose ALL your data.

Now, if you add one single 2TB disk to your zpool, you will have two groups: one raidz1 and one single disk. If that single disk dies, you have lost ALL your data.

Better to add a new group which is a mirror. So you have 4 x 1TB disks in raidz1, and another group which is a mirror of two 2TB disks. Now, you can loose one disk in the 2TB group, and loose one disk in the raidz1 group - without problems.



All this is explained. Read the zfs wikipedia entry.