Product and version information:
1.The storage array and the application server were connected through iSCSI links. A LUN was mapped to the Asianux host, and the a read/write test was performed by using the IOmeter.
2.During the read/write operations, an iSCSI link-down occurred (caused by a cable removal or unexpected power-off). The host CPU utilization was close to 100% and the host was not responding even to SSH or KVM login attempts.
1.Attempt to restore the iSCSI connections and wait 5 minutes for the host to start responding.
2.If the host is still not responding, restart the host.
1.Dynamo on Linux has an unlimited retry mechanism. When a slave block device returned an I/O error to upper-layer applications, Dynamo retried this failed I/O immediately, but the iSCSI driver returned this retry I/O as an error.
2.The above situation was a logical infinite loop. This infinite loop resulted in a CPU utilization of close to 100%.
The red rectangle in Figure1 shows the CPU utilization.
3.When the CPU utilization was close to 100%, the host may not respond to any external events.
We ran the same test on a RedHat5.4 host, and the same symptoms occurred.