Recovering a Failed LSI or Intel RAID Array
This article will show you how to recover a failed RAID 5 array on an Intel or LSI hardware RAID controller. The same or similar process can also be used with other RAID arrays such as RAID 1 or RAID 6.
It is important to understand first how drive configuration information is stored, and what a "foreign configuration" is, as you may see messages about this appear.
What is a Foreign Configuration?
Intel or LSI Hardware RAID controllers store RAID volume configuration information on both the drives and the controller. When the system is booted or a drive is inserted, the drives and configurations are examined and any configurations that don't match each other are flagged as a foreign configuration. The RAID controller will use its own configuration as the master record, to identify which configurations are invalid.
All physical drives configuration information contains a list of the drives involved in the associated logical drive.
What's the difference between Optimal, Degraded, Critical and Offline?
RAID controllers use these terms to show the health of the logical drive.
For example, RAID6 arrays can lose up to two drives. The loss of one drive will result in the logical drive being reported as degraded, not critical.
Scenario 1 - The system is booted but not all of the drives are plugged in, possibly due to a loose cable.
Messages such as the one above require prompt action:
Scenario 2 - A drive has failed, but now a message about a Foreign Configuration has appeared
Hard drives which encounter problems such as bad blocks or a controller fault may stop being able to be detected. The drive may then become "available" again, perhaps after the drive has reallocated the bad blocks. However, when the drive failed, the RAID card will have written a configuration update to itself and the remaining drives, notifying the failed drive. The configuration on the failed drive is now out of date and does not match the other drives, so it is flagged as having a foreign configuration.
Scenario 3 covers importing a foreign configuration.
Scenario 3 - The drive was disconnected accidentally, my array is offline and I need to recover it.
Disconnected drives will either be marked as Foreign, or Unconfigured Bad. Unconfigured bad drives cannot be have the foreign configuration imported until you mark the drive as "Unconfigured good".
Foreign drives detected on the RAID card boot may be flagged as below.
In this instance, either Press F, or better still, press CTRL+G to enter the RAID BIOS and manage the foreign configuration process.
Some older RAID cards may allow you to Import a foreign configuration without Previewing it. However we recommend you always preview the configuration to be imported and check that all logical drives - including those that have no problem - are correctly shown.
If you have different drives with different foreign configurations then you may have multiple choices to try and import. Try "All Configurations" first. If this does not work, try each configuration in turn, making sure you preview it first. It is likely that only the configuration from the last drive that failed will be importable.
Scenario 4 - I'm Running RAID 5 and my system crashed. I appear to have had two hard drives fail.
This can happen especially if you have a hot-spare drive. When the first drive fails, the RAID card will start rebuilding onto the spare. The unusual workload may cause another weak drive to then experience a failure.
In this scenario you may not may not get messages about a foreign configuration. If you do not, or if the foreign configuration does not import, follow the steps below:
In All Situations
What Can I do to Minimise the Chances of Unexpected Failures?