replication is very slow when it reaches about 90% of total items

Install ms 1.6.5.3r-12 on node 52, 53 and 55.
Load 6M keys with 2K/key to node 52
Run a load on node 52 using memcachetest
/memcachetest -h localhost:11211 -i 200000 -c 1000000 -K test_ -m 1000 -M 1500 -t 4
Add node 53 and 55 to node 52.
Rebalance
After rebalance is done, view stats all and see replication is very slow when it reaches about 90% of total keys.
./stats 10.2.1.52:11211 all
When replication is done. Disconnnect internet connection on node 53.
Fail over node 53 and rebalance.
After rebalance is done, view stats all and see replication is still very slow when it reaches about 90% of total keys.
Check tap connection, see paused is 1 on node 52
http://screencast.com/t/eXAyDshY1

root@ubuntu1004-32:/opt/membase/bin/ep_engine/management# ./stats 10.2.1.52:11210 tap
ep_tap_ack_grace_period: 300
ep_tap_ack_interval: 1000
ep_tap_ack_window_size: 10
ep_tap_backoff_period: 1
ep_tap_bg_fetch_requeued: 0
ep_tap_bg_fetched: 22067848
ep_tap_bg_load_avg: 472
ep_tap_bg_max_load: 900038
ep_tap_bg_max_pending: 500
ep_tap_bg_max_wait: 125891211
ep_tap_bg_min_load: 10
ep_tap_bg_min_wait: 12
ep_tap_bg_num_samples: 2194430
ep_tap_bg_wait_avg: 206088
ep_tap_count: 1
ep_tap_deletes: 0
ep_tap_fg_fetched: 27932060
ep_tap_keepalive: 300
ep_tap_noop_interval: 20
ep_tap_throttled: 5203693
ep_tap_total_fetched: 50004544
ep_tap_total_queue: 2208
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:ack_log_size: 1106
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:ack_playback_size: 1108
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:ack_seqno: 7824103
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:ack_window_full: false
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:bg_backlog_size: 2197
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:bg_jobs_completed: 4940965
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:bg_jobs_issued: 4940965
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:bg_queue_size: 0
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:bg_queued: 4940965
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:bg_result_size: 0
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:bg_results: 0
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:bg_wait_for_results: false
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:complete: false
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:connected: true
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:empty: false
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:flags: 20 (ack,vblist)
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:has_item: false
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:has_queued_item: true
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:idle: false
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:last_walk: 16500
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:num_tap_nack: 317235
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:num_tap_tmpfail_survivors: 317235
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:paused: 1
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:pending_backfill: false
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:pending_disconnect: false
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:pending_disk_backfill: true
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:qlen: 2208
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:qlen_high_pri: 0
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:qlen_low_pri: 0
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:rec_fetched: 3139629
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:recv_ack_seqno: 7823000
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:suspended: false
eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:vb_filter:

{ [27,93], 95, 96, 99, 100, 103, 104, 107, 108, 111, 112, 115, 116, 119, 120, 123, 124, 127, 128, 131, 132, 135, 136, 139, 140, 143, 144, 147, 148, 151, 152, 155, 156, 159, 160, 163, 164, 167, 168, 171, 172, 175, 176, 179, 180, 183, 184, 187, 188, 191, 192, 195, 196, 199, 200, 203, 204, 207, 208, 211, 212, 215, 216, 219, 220, 223, 224, 227, 228, 231, 232, 235, 236, 239, 240, 243, 244, 247, 248, 251, 252, 255, 256, 259, 260, 263, 264, 267, 268, 271, 276, 294, 300, 318, 324, 342, 348, 366, 372, 390, 396, 414, 420, 438, 444, [683,1023] }

eq_tapq:r-ns_1@10.2.1.55-ns_1@10.2.1.52-1300923869.758056:vb_filters: 512

root@ubuntu1004-32:/opt/membase/bin/ep_engine/management# ./stats 10.2.1.55:11210 tap
ep_tap_ack_grace_period: 300
ep_tap_ack_interval: 1000
ep_tap_ack_window_size: 10
ep_tap_backoff_period: 1
ep_tap_bg_fetch_requeued: 0
ep_tap_bg_fetched: 12904738
ep_tap_bg_load_avg: 1226
ep_tap_bg_max_load: 1069273
ep_tap_bg_max_pending: 500
ep_tap_bg_max_wait: 279732320
ep_tap_bg_min_load: 10
ep_tap_bg_min_wait: 8
ep_tap_bg_num_samples: 737331
ep_tap_bg_wait_avg: 763807
ep_tap_count: 1
ep_tap_deletes: 0
ep_tap_fg_fetched: 17165129
ep_tap_keepalive: 300
ep_tap_noop_interval: 20
ep_tap_throttled: 2489170
ep_tap_total_fetched: 30072276
ep_tap_total_queue: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:ack_log_size: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:ack_playback_size: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:ack_seqno: 7546820
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:ack_window_full: false
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:bg_backlog_size: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:bg_jobs_completed: 3937089
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:bg_jobs_issued: 3937089
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:bg_queue_size: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:bg_queued: 3937089
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:bg_result_size: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:bg_results: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:bg_wait_for_results: false
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:complete: false
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:connected: true
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:empty: true
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:flags: 20 (ack,vblist)
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:has_item: false
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:has_queued_item: false
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:idle: true
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:last_walk: 16226
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:num_tap_nack: 341200
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:num_tap_tmpfail_survivors: 341200
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:paused: 1
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:pending_backfill: false
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:pending_disconnect: false
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:pending_disk_backfill: true
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:qlen: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:qlen_high_pri: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:qlen_low_pri: 0
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:rec_fetched: 3835991
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:recv_ack_seqno: 7546819
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:suspended: false
eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:vb_filter:

{ [0,26], 94, 97, 98, 101, 102, 105, 106, 109, 110, 113, 114, 117, 118, 121, 122, 125, 126, 129, 130, 133, 134, 137, 138, 141, 142, 145, 146, 149, 150, 153, 154, 157, 158, 161, 162, 165, 166, 169, 170, 173, 174, 177, 178, 181, 182, 185, 186, 189, 190, 193, 194, 197, 198, 201, 202, 205, 206, 209, 210, 213, 214, 217, 218, 221, 222, 225, 226, 229, 230, 233, 234, 237, 238, 241, 242, 245, 246, 249, 250, 253, 254, 257, 258, 261, 262, 265, 266, 269, 270, [272,275], [277,293], [295,299], [301,317], [319,323], [325,341], [343,347], [349,365], [367,371], [373,389], [391,395], [397,413], [415,419], [421,437], [439,443], [445,682] }

eq_tapq:r-ns_1@10.2.1.52-ns_1@10.2.1.52-1300923870.101719:vb_filters: 512