Leap second and VIO Server

Answer

Occasionally a second is added at the end of the day to adjust the Coordinated Universal Time and keep it close to Solar Time. Certain application, requiring a strong time synchronization, may suffer from this time change.

Last time a leap second occurred was on June 30, 2015, and we'll see the next leap second on December 31, 2016.

As documented in the technote T1022057, AIX, and by extension VIOS, does not have and never had any direct awareness of the leap second. There have been several leap seconds over the years through the history of AIX, with no known AIX issues reported. The same applies for VIOS. Last time the leap second occurred, there was no impact on VIOS.

The main VIOS features (vscsi / vfc hosting, SEA, LPM...) are using many timers but none of these timers are related to the date/time of the VIOS, which means a single second added will not impact those timers.

Within an SSP cluster configuration there's more timers added (electing DBN, MSP...), but the lease time for those component are much more longer than a second. Which means even if the clock moves forward by one more second, it should be transparent for VIOS.

There's only 2 different possibilities for VIOS :

• The VIOS does not require a strong time synchronization, so there's no NTP setup on the VIOS. When the leap second will occur the VIOS will just have a 1 second difference with UTC, but this won't affect VIOS functionality.

• The VIOS needs to be synchronized (which is also recommended for SSP cluster), in that case NTP client on VIOS will slowly adjust the system clock to stay in sync with the time server.