What can cause mongodb replset to be so slow?

Question

This is the first sync to the primary node:

2017-03-03T02:26:22.035+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 283940/5543302 5% (documents copied)
2017-03-03T02:36:17.984+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 564884/5543302 10% (documents copied)
2017-03-03T02:48:31.792+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 849813/5543302 15% (documents copied)
2017-03-03T03:02:14.751+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 1138030/5543302 20% (documents copied)
2017-03-03T03:14:10.938+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 1474370/5543302 26% (documents copied)
2017-03-03T03:32:53.645+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 1846885/5543302 33% (documents copied)
2017-03-03T03:46:50.211+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 2207922/5543302 39% (documents copied)
2017-03-03T03:56:41.963+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 2568851/5543302 46% (documents copied)
2017-03-03T04:08:13.513+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 2921563/5543302 52% (documents copied)
2017-03-03T04:27:33.926+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 3230454/5543302 58% (documents copied)
2017-03-03T05:09:17.002+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 3408499/5543302 61% (documents copied)
2017-03-03T05:27:33.817+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 3531029/5543302 63% (documents copied)
2017-03-03T06:12:44.765+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 3747209/5543302 67% (documents copied)
2017-03-03T06:49:28.263+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 3894147/5543302 70% (documents copied)
2017-03-03T07:46:30.452+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 4001247/5543302 72% (documents copied)
2017-03-03T08:06:56.895+0100 I -        [repl writer worker 3]   prodbase.offer collection clone progress: 4108649/5543302 74% (documents copied)

All servers are in the same datacenter with 250 Mbit/s between them.

Have you checked your disk IO? – Vince Bowdren Mar 30 '17 at 09:27 — Vince Bowdren, Mar 30 '17 at 09:27

score 0 · Answer 1 · answered Mar 03 '17 at 13:17

0

suggestion: Move to 3.4.x

Big improvements with the initial sync

Otherwise, all depend on how much data you have on the primary

Another solution to avoid this is to

backup your primary
restore primary onto your secondary
Config and start the replication

answered Mar 03 '17 at 13:17

Philippe Courtois

1
1

We have 3.4.1 on all instances. I understand that it could be much faster to copy directory, but didn't expect that native sync is so slow. – Lisio Mar 03 '17 at 13:59
How big is your data ? In our cases we have about 10Gb of data and initial sync takes less than 45 Sec to 1 minute. On a node 800KM away it takes 2-3 minutes. – Philippe Courtois Mar 03 '17 at 14:00
Size of that collection is 55Gb (compacted to 20Gb by WiredTiger). – Lisio Mar 03 '17 at 14:17

What can cause mongodb replset to be so slow?

1 Answers1