Massive increase in disk write queue size on both SSD and HDD.

The issue happens on both Windows and Linux. The links below are for Windows runs.
Comparison of the runs on SSD:
http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=zeus_251-1083_97c_access&snapshot=zeus_302-1503_047_access

disk write queue report on SSD:
http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=zeus_251-1083_97c_access&snapshot=zeus_302-1503_047_access#zeus_251-1083_97c_accesszeus_302-1503_047_accesszeus_251-1083_97czeus_302-1503_047bucket-1disk_write_queue

Comparison of the runs on HDD:
http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=hermes_251-1083_7e8_access&snapshot=hermes_302-1503_4eb_access

disk write queue report on HDD:
http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=hermes_251-1083_7e8_access&snapshot=hermes_302-1503_4eb_access#hermes_251-1083_7e8_accesshermes_302-1503_4eb_accesshermes_251-1083_7e8hermes_302-1503_4ebbucket-1disk_write_queue