@vsomani@hortonworks.com NameNode disk failure. There are couple of if's 1 - HA + RAID 10 If HA is in place then failover to Passive (Assuming that active NN disk failed) + if RAID 10 is configured for NN then you are safe and have enough time to replace failed disk. "When a single disk in a RAID 10 disk array fails, the disk array status changes to Degraded. The disk array remains functional because the data on the Failed disk is also stored on the other member of its mirrored pair.When ever a disk fails, replace it as soon as possible. If a hot spare disk is available, the controller can rebuild the data on the disk automatically. If a hot spare disk is not available, you will need to replace the failed disk and then initiate a rebuild. " 2 scenario - No HA, No RAID but NN backup in place + "dfs.namenode.name.dir" is writing to multiple disks. You are safe as NN metadata writing to multiple disks so you can remove the disk location from Ambari and let operator recover the disk failure. 3 scenario - Bad design : No HA, No RAID, dfs.namenode.name.dir writing to single disk Cluster is down. Backup everything that you can from NN. Let operator replace the disk. Restore the backup and then starts the troubleshooting process. Good disucssion here 1
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