Hi Taz,

I just found a KB on this,please have a look:

emc85525

Thanks

Jyothi

Resolution:

Celerra and VNX File will not follow the leap second adjustment automatically due to the infrequent schedule decided by IERS. However, there is no impact on Celerra or VNX File systems.

Customers still concerned about this should use NTP servers to synchronize the time in Celerra/VNX (and all other computer equipment).

See also:

197322 : Product Impacts of Upcoming Leap Second UTC adjustment on June 30th 2015
https://support.emc.com/kb/197322

Lists a number of EMC products and if they are impacted or not you may find helpful.

I was concerned about Cisco and Brocade switches having this issue but as per the above KB they are not impacted. More research i found

Brocade: FAQ4555

Cisco: http://www.cisco.com/go/leapsecond and https://tools.cisco.com/bugsearch/bug/CSCut22182

Basically Cisco and Brocade switches are unaffected.

Thanks

Allan (EMC)

Looks like there is a small risk for the CS's even with NTP enabled per 197322:

Updated 5/15/15: VNX1 systems using NTP on the Control Station have a very small risk of a Control Station hang when the leap second change occurs (no issues reported during the last 2012 Leap Second change). Risk averse customers have two options. Option 1, disable NTP on the Control Station prior to the Leap Second change and re-enable it after the change. Option 2, upgrade to the latest VNX1 OE revision prior to June 30. Please contact EMC Support to schedule an OE upgrade

There is another "option;" put the Control Station (for example) into Slew Mode.  This would also work for various sorts of Unix/Linux hosts running less than version 4.2.6 of NTP.