[blue68f100]

You do not want to do any thing to break the array if you want your data back.

You may remove the failed HD if you like. Just make sure you get the right one, other wise all is lost. 2 outs and your out.

If you already had a hot spare normally it only takes a reboot of the snap to start the process. If not change it to Hot Spare.

Power down and replace the failed HD.
Boot the snap
Once up wait about 5 min
Migrate to the drive configuration page.
Select the newly installed HD, set it as a Hot Spare.
Then walk away. It my take the snap many hours to init the drive and start the array rebuild. Be Patient.
If it hangs in the 5% area, this is the area where the snap stores all of it tables. NOT GOOD.
If it does it may indicate another HD is having problem.