How to remove Yellow Alert on Freenas

Sometimes we inevitably encounter a Yellow Alert in FreeNAS. Good thing FreeNas has its own GUI to easily inform the administrator about its status.

can be found at the upper right corner of the browse
when you click it, a message will show

WARNING: The volume mypool (ZFS) status is UNKNOWN: One or more devices has experienced an unrecoverable error. An attempt was made to correct the error. Applications are unaffected.Determine if the device needs to be replaced, and clear the errors using 'zpool clear' or replace the device with 'zpool replace'.

first, you need to click Shell from lower left corner
then type zpool status -v
to show the zpool status in detail

then a detailed zpool status will shown

then type zpool clear mypool(name of your pool) gptid/kfhauyr08hj-5803-sdfjal(name of array)

That's it, i hope it helped you.