Limitations of BackupNode (BN)
Maximum of one BackupNode per NN
– Support only two-machine failure
NN does not forward block reports to BackupNode
Time to restart from 2 GB image, 20M files + 40 M blocks
– 3 – 5 minutes to read the image from disk
– 30 min to process block reports
– BN will still take 30 minutes to failover!
