How to analyze big report archives?

My piwik database is suddently rapidly growing (now 30gb). I have not upgraded Piwik and although we recently receive more traffic, the growth seems out of proportion.

I am looking for help in reducing the database size and/or to find out where this growth is coming from.

The privacy page reports: Current database size: 30 G
I have ran the diagnostics:analyze command on the biggest archive (which is listed as 19gb in phpmyadmin)

[details=Output of: diagnostics:analyze-archive-table 2017_01
]Statistics for the archive_numeric_2017_01 and archive_blob_2017_01 tables:

SEE: +-------------------------------------------+------------+---------------+------ - Pastebin.com (too big for this forum)

[/details]

How to read the diagnostics? Are any of these numbers significant?

Total # Invalidated Archives: 15059
Total # Temporary Archives: 615
Total # Error Archives: 7

[details=Output from Diagnostic -> Database usage]Tracking 6 websites (Total: 2,509,806 visits, 20,957,656 pageviews, 48,039,817 actions, 0 revenue)

Tracker Tables

TABLE DATA SIZE INDEX SIZE ROW COUNT
piwik_log_action 725 M 58.6 M 594,573
piwik_log_conversion 16 K 32 K -
piwik_log_conversion_item 16 K 16 K -
piwik_log_link_visit_action 4.4 G 3 G 34,273,109
piwik_log_visit 497 M 382.6 M 1,744,611
Total 5.6 G 3.5 G 36,612,293

Report Tables
TABLE DATA SIZE INDEX SIZE ROW COUNT
piwik_archive_blob_2017_12 16 K 16 K -
piwik_archive_blob_2017_11 16 K 16 K -
piwik_archive_blob_2017_10 16 K 16 K -
piwik_archive_blob_2017_09 16 K 16 K -
piwik_archive_blob_2017_08 16 K 16 K -
piwik_archive_blob_2017_07 16 K 16 K -
piwik_archive_blob_2017_06 162.1 M 2.3 M 32,077
piwik_archive_blob_2017_05 667.3 M 7 M 55,323
piwik_archive_blob_2017_04 394.1 M 9 M 14,770
piwik_archive_blob_2017_03 265.1 M 6 M 12,566
piwik_archive_blob_2017_02 207.1 M 5 M 12,412
piwik_archive_blob_2017_01 18.6 G 75.3 M 2,164,049
piwik_archive_blob_2016_12 85 M 3 M 12,101
piwik_archive_blob_2016_11 113 M 3 M 12,837
piwik_archive_blob_2016_10 75 M 3 M 5,216
piwik_archive_blob_2016_09 81 M 4.1 M 5,886
piwik_archive_blob_2016_08 8.1 M 208 K 841
piwik_archive_blob_2016_07 16 K 16 K -
piwik_archive_blob_2016_06 16 K 16 K -
piwik_archive_blob_2016_05 16 K 16 K -
piwik_archive_blob_2016_04 16 K 16 K -
piwik_archive_blob_2016_03 16 K 16 K -
piwik_archive_blob_2016_02 16 K 16 K -
piwik_archive_blob_2016_01 45 M 128 K 240
piwik_archive_blob_2015_12 16 K 16 K -
Total 20.7 G 118.3 M 2,328,318
1-25 of 67

Metric Tables
TABLE DATA SIZE INDEX SIZE ROW COUNT
piwik_archive_numeric_2017_12 16 K 32 K -
piwik_archive_numeric_2017_11 16 K 32 K -
piwik_archive_numeric_2017_10 16 K 32 K -
piwik_archive_numeric_2017_09 16 K 32 K -
piwik_archive_numeric_2017_08 16 K 32 K -
piwik_archive_numeric_2017_07 16 K 32 K -
piwik_archive_numeric_2017_06 1.3 M 2.5 M 13,900
piwik_archive_numeric_2017_05 4 M 7 M 14,914
piwik_archive_numeric_2017_04 5 M 8 M 6,160
piwik_archive_numeric_2017_03 3 M 5 M 7,446
piwik_archive_numeric_2017_02 3 M 5 M 8,080
piwik_archive_numeric_2017_01 17.1 M 19.1 M 171,825
piwik_archive_numeric_2016_12 2 M 3 M 3,489
piwik_archive_numeric_2016_11 2 M 3 M 3,125
piwik_archive_numeric_2016_10 3 M 4 M 2,095
piwik_archive_numeric_2016_09 2.1 M 7.1 M 2,547
piwik_archive_numeric_2016_08 128 K 176 K 661
piwik_archive_numeric_2016_07 16 K 32 K -
piwik_archive_numeric_2016_06 16 K 32 K -
piwik_archive_numeric_2016_05 16 K 32 K -
piwik_archive_numeric_2016_04 16 K 32 K -
piwik_archive_numeric_2016_03 16 K 32 K -
piwik_archive_numeric_2016_02 16 K 32 K -
piwik_archive_numeric_2016_01 16 K 32 K 157
piwik_archive_numeric_2015_12 16 K 32 K -
Total (learn more) 43 M 64.6 M 234,399

Other Tables
TABLE DATA SIZE INDEX SIZE ROW COUNT
piwik_access 16 K 0 M 6
piwik_goal 16 K 0 M -
piwik_logger_message 16 K 0 M -
piwik_log_profiling 16 K 16 K -
piwik_option 176 K 16 K 217
piwik_plugin_setting 16 K 16 K 6
piwik_sequence 16 K 0 M 67
piwik_session 16 K 0 M -
piwik_site 16 K 0 M -
piwik_site_setting 16 K 0 M -
piwik_site_url 16 K 0 M -
piwik_user 16 K 16 K 4
Total (learn more) 352 K 64 K 300

[/details]

Note that I have already setup auto archiving.
Any pointers on whether this is looking healthy or not are very welcome.