If tail drops are seen on any router/ switch and the traffic is not close to the line rate, then the drop is due to microbursts in traffic.

Tail drops even when traffic is not close to line rate.

In the case of EX4300, the following config can be used to set the shared buffer setting on egress to 100%.

set class-of-service shared-buffer percent 100

The below commands can be used for verification.

(vty)# show halp-cos buffer ifd_name ge-0/0/0
Port: ge-0/0/0 IF Index: 649  BCM Port: 14 Base QIndex: 104
Q No   Min_Alloc   Alpha    SharedAccess   Min_Used   Sh_Used
--------------------------------------------------------------
 0      178          7          YES          178     5638 <<<<<<<< shared buffer usage.

Sh_used column represents the use of shared buffer. Pl compare this output before and after applying the config for comparison.