Oracle Linux and Unbreakable Enterprise Kernel Support Notes

3 Recommendations, Limitations, and Known Issues
This chapter contains recommendations, limitations, and known issues with the use of Oracle Linux
and Unbreakable Enterprise Kernel on HP DL980 servers.
Recommendations
The following recommendations from HP for using Oracle Linux and Unbreakable Enterprise Kernel
on HP DL980 servers should be observed.
Upgrading from earlier OL versions
The OL Release Notes and other previous versions, included with each Oracle Linux product
release, contain upgrading instructions and suggestions. To locate these documents, see “Installation
documentation” (page 8).
Limitations
The following section describes the limitations of Oracle Linux and Unbreakable Enterprise Kernel
on HP DL980 servers.
Supported kernel memory maximum
The RHEL 5.x compatible kernel supports a maximum memory size of 4 TB, which is also supported
by HP.
Known Issues
This section contains known issues
Known Issues with UEK2.6.39-100:
• Large I/O configurations may report call trace or cause a system hang when a system reboot
is initiated (OL5.7, OL5.8, OL6.2)
When rebooting the system, occasionally a call trace will be printed out reporting a bad IRQ.
In some cases, the system may hang when trying to reboot. These events are observed with
systems loaded with large numbers of I/O cards. This hang will require the user to force the
system off and back on. At this time, there is no fix.
• Kernel is not able to reserve more than 482M of memory for crash dump. Crash dump on
large memory systems may need 512M or more reserved memory to function properly. At
this time, UEK2.6.39-100 cannot reserve memory larger than 483M, and therefore crash
dump on large memory systems may not function properly.
• Qlogic P3+ cards (HP CN1000Q and HP NC523SFP) may report firmware hangs while
under heavy stress.
While under heavy stress, the following message may be reported by the qlcnic driver:
nl
qlcnic 0000:56:00.0: firmware hang detected
At that time, the interface will go down and back up to allow for a device reset. This may
cause a temporary interruption in communication with the interface.
• "BUG: soft lockup" may be reported during system boot.
When “console=ttyS1” (which defaults to using 9600 baud rate) is added as a kernel boot
parameter or is specified in the grub.conf file, a soft lockup may be reported on the boot,
or in some cases the system may hang. To avoid the soft lockup or system hang, configure
10 Recommendations, Limitations, and Known Issues