InfluxDB 1.8 – All data disappeared after changing retention policies

InfluxDB 1
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Hi there,

I’m trying to understand what happened with my InfluxDB instance because all data prior to Feb 4 disappeared, and I suspect it may be related to changes I made to the retention policies.

My version:

InfluxDB shell version: 1.8.10

System context

Earlier that day some system maintenance was done:

475 2026-02-04 07:54:54 : apt update
478 2026-02-04 07:55:26 : apt upgrade
483 2026-02-04 08:01:18 : apt autoremove

InfluxDB logs

Later in the logs I can see this error related to disk space:

Feb 04 09:30:00 monitor influxd-systemd-start.sh[521]: ts=2026-02-04T08:30:00.005840Z lvl=info msg="Executing query" log_id=0zVLdLXl000 service=query query="SELECT mean(used_percent) AS used_percent FROM telegraf_intern.autogen.disk WHERE (host =~ /^proxmox$/ AND fstype = 'ext4') AND time >= now() - 6h AND time <= now() - 30s GROUP BY time(1m), path"

Feb 04 09:30:00 monitor influxd-systemd-start.sh[521]: ts=2026-02-04T08:30:00.306211Z lvl=info msg="Error writing snapshot" log_id=0zVLdLXl000 engine=tsm1 error="error opening new segment file for wal (1): write /var/lib/influxdb/wal/telegraf/autogen/1709/_00024.wal: no space left on device"

Feb 04 09:30:01 monitor influxd-systemd-start.sh[521]: ts=2026-02-04T08:30:01.306270Z lvl=info msg="Error writing snapshot" log_id=0zVLdLXl000 engine=tsm1 error="error opening new segment file for wal (1): write /var/lib/influxdb/wal/telegraf/autogen/1709/_00024.wal: no space left on device"

So at that moment the disk was full.

Investigation commands

Later in the timeline, I found this in the history:

470 2026-02-04 08:18:09 : ncdu /

This particular one was earlier, during maintenance, but I don’t think anyone deleted the information from using -d in the ncdu interface.

460 2026-02-04 10:47:11 : influx
461 2026-02-04 10:47:37 : df -h
462 2026-02-04 10:52:58 : du -sh /var/lib/influxdb/data/*
463 2026-02-04 10:54:14 : du -sh /var/lib/influxdb/data/telegraf/* | sort -h
464 2026-02-04 10:54:14 : du -sh /var/lib/influxdb/data/telegraf_intern/* | sort -h
465 2026-02-04 10:54:39 : du -sh /var/lib/influxdb/data/telegraf/autogen/* | sort -h
466 2026-02-04 10:54:39 : du -sh /var/lib/influxdb/data/telegraf_intern/autogen/* | sort -h

Retention policy changes

“Scrolling up” in the InfluxDB shell history, these commands were executed (in this order). Unfortunately I cannot know the when or how much time passed between them.

(I mean that I cannot know either the day or the time when they were executed in relation to the rest of the logs)

USE telegraf;
CREATE RETENTION POLICY "18months" ON "telegraf" DURATION 78w REPLICATION 1 DEFAULT;

USE telegraf_intern;
CREATE RETENTION POLICY "18months" ON "telegraf_intern" DURATION 78w REPLICATION 1 DEFAULT;

USE icinga2;
CREATE RETENTION POLICY "18months" ON "icinga2" DURATION 78w REPLICATION 1 DEFAULT;

SHOW RETENTION POLICIES ON telegraf;
SHOW RETENTION POLICIES ON telegraf_intern;
SHOW RETENTION POLICIES ON icinga2;

DROP RETENTION POLICY "autogen" ON telegraf;
DROP RETENTION POLICY "autogen" ON telegraf_intern;
DROP RETENTION POLICY "dades_18_mesos" ON telegraf_intern;
DROP RETENTION POLICY "autogen" ON icinga2;

What I was trying to do

I noticed there were several retention policies:

  • autogen

  • dades_18_mesos

  • others

InfluxDB seemed to be storing more than 18 months of data, so I assumed the policies might be overlapping.

My reasoning was:

  • autogen has infinite retention

  • dades_18_mesos had 18 months for example

So I thought that since autogen was infinite, it effectively included the 18-month data anyway.

Because of that, I:

  1. Created new 18-month retention policies

  2. Set them as DEFAULT

  3. Then dropped the autogen policies

I assumed that data within the new 18-month policies would remain, and only the rest would be deleted.

Problem

All data prior to Feb 4 disappeared :sob:

Question

Did dropping the autogen retention policy delete all the data that was stored under it?

Even though I created the new 18months retention policy before dropping autogen, could that still have caused the loss of historical data?

Or could the disk full situation have played a role in this? or even the “upgrade” ¿?

Any clarification about how InfluxDB handles retention policy deletion and data migration (or lack of it) would be very helpful

2

Dropping the autogen retention policy indeed deleted all the data that was stored under it. This is explained with a warning in the documentation: “Dropping a retention policy will permanently delete all measurements and data stored in the retention policy.” The logic here is that if you want to change the duration of a retention policy, you can use ALTER RETENTION POLICY. A retention policy is the definition of how and how long to keep your data, so if you delete the entire policy, you also delete the data it was retaining.