First, you need to post the zpool status output in CODE tags. The formatting of the text is CRUCIAL to understanding what your pool is doing. Consider these 2 outputs:
Code:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
raidz1-0 ONLINE 0 0 0
gptid/6fbb91d5-4a95-11e2-bca4-0015171496ae ONLINE 0 0 0
gptid/70448fd2-4a95-11e2-bca4-0015171496ae ONLINE 0 0 0
gptid/70c0c7b3-4a95-11e2-bca4-0015171496ae ONLINE 0 0 0
gptid/713de0d5-4a95-11e2-bca4-0015171496ae ONLINE 0 0 0
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
raidz1-0 ONLINE 0 0 0
gptid/6fbb91d5-4a95-11e2-bca4-0015171496ae ONLINE 0 0 0
gptid/70448fd2-4a95-11e2-bca4-0015171496ae ONLINE 0 0 0
gptid/70c0c7b3-4a95-11e2-bca4-0015171496ae ONLINE 0 0 0
gptid/713de0d5-4a95-11e2-bca4-0015171496ae ONLINE 0 0 0
The first output is 4 disks in a RAIDZ1.
The second output is 3 disks in a RAIDZ1 + 1 disk striped. Money says you have a striped disk at the end and the GUI has noticed that extra space. See how important a single "space" is? Imagine all the noobs that are so lost because they aren't used to that level of attention required and that kind of importance for a space in Windows. :p
First: You cannot remove that stripe disk from the pool now no matter what. If you can destroy and recreate the pool that's your option. But your bigger problem is that if that disk fails right now you will lose your entire pool. Not just
some data, the entire pool. So what you need to do now is get another disk and mirror that disk so you have some redundancy ASAP. This will require you to do it from the CLI since you can't add a mirror disk to a vdev from the GUI. This should be
very high on your priority. Searching around the forums will allow you to find the appropriate command to add the mirror. We've had some people lose their pool in this way before they could get their replacement disk, so don't waste time!
Second: There is no way to take 2 pools and combine them into 1 big iscsi disk.
Third: You cannot add single disks to a vdev. This is explained in my presentation(link in my sig). You can never add disks to a vdev once it has been created with one exception; adding disks to a vdev to make mirrors. You were probably hoping to add another disk to "expand" the zpool. You can't do that without giving up redundancy. That's why we tell people to oversize their zpool because adding more space later is not trivial. If you don't oversize your pool you'll be forced to buy multiple disks to ensure redundancy. This is a limitation of ZFS and there is no fix ever coming for this. It's not considered a problem since ZFS is considered an enterprise class product. Typically, buying a dozen or more disks isn't a problem for corporations.
