how to import a detached volume with status UNAVAIL

[ashokmedia]

Your zpool history is only showing the freenas-boot pool ... although since the other one is in an exported state that's probably to be expected.

But looking at the zdb output we can see that your pool was indeed created with four striped vdevs. All four disks are directly from the root.

is there any way to recover?

 

[garm]

You have two options, restore from backup or revive the lost disk and make it a part of the pool long enough to take a backup so you can restore to a new pool (preferably with redundancy)