Inside system logs (/var/log/messages), you may see some message like this on a system running a RAID controller (this one is from a PERC 5/i on a Dell PowerEdge server) :
mptbase: ioc0: WARNING – IOC is in FAULT state (1600h)!!!
mptbase: ioc0: WARNING – Issuing HardReset from mpt_fault_reset_work!!
mptbase: ioc0: Initiating recovery
mptbase: ioc0: WARNING – IOC is in FAULT state!!!
mptbase: ioc0: WARNING – FAULT code = 1600h
mptbase: ioc0: Recovered from IOC FAULT
mptbase: ioc0: WARNING – mpt_fault_reset_work: HardReset: success
This indicate either a drive is failing or a driver bug. May not be critical at all, but should be taken seriously! Some time the system may hang after displaying this.
If you see a failed message about the recovery/hard reset or a device offlined soon after this message, it’s definitely a failed hard disk. In any situation, have a look at the storage device manager for more information (in this case, since this is a Dell server, we may have a look at OpenManage).