Software Raid in 2.4: Bug in raid code? - reconstruction problems: reconstruction stops and system lockup
Jeff Folts
kernel 2.4.2 and 2.4.3 SMP
Scenario:
Reconstruction Stops:
During bootup, if reconstruction of large arrays coincides with file system checks of large file systems, the reconstruction will stop during the file system checks and does not restart, even when the file system checks are done and the system is idle.
System Lockup:
When the reconstruction stops, the KBytes/sec rate of reconstruction eventually goes to zero. It appears that when the rate goes below the minimum reconstruction rate as specified in /proc/sys/dev/raid/speed_limit_min, raid kernel threads seem to consume all available CPU causing what appears to be a lockup. The system still responds, but so slowly, it is practically locked up. When the array reconstruction is stuck on an array, the recovery thread runs at 100% CPU, whether speed_limit_min is 0 or not.
Lockup Workaround:
If speed_limit_min is set to zero, the apparent lockup does not occur, but the reconstruction remains stopped until the array that is stuck is stopped and restarted.