Oracle VM Oracle Linux 5 UEK1 PVM guest may experience I/O hang to one disk device or connectivity loss to one network device
Last updated on APRIL 29, 2016
Applies to:Oracle VM - Version 2.1 and later
*** Last checked for currency: 29 Apr 2016 ***
An Oracle VM Oracle Linux 5 (OL5) Paravirtualised (PVM) guest running the Unbreakable Linux Kernel Release 1 (2.6.32-*.el[5,6]uek) may sporadically experience I/O hang to only one storage device.
Alternatively, the guest may eperience loss of network connectivity to only one network device.
If the guest Virtual Machine (VM) is running fence-capable software e.g. Oracle Real Applications Cluster (RAC)/Grid Infrastructure (GI), OCFS2, etc., the inability to perform disk or network heartbeat to/via an affected device may result in node fence (cluster eviction, reboot).
The issue is unpredictable, but known to affect guest VMs under high I/O load, as well as idle guests.
Symptoms of the issue include:
- sudden sustained iostat 100% %iowait for the affected device and without any r/w activity
- ever increasing iostat avgqu-sz
- elevated system load average
- system log denotes repeated hung task messages with call stack e.g. INFO: task oracle:12345 blocked for more than 120 seconds
- sudden sustained loss of network connectivity to only one network device
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