Apparently some old closed indices are no longer holding information [1]
Analyze further and delete those if indeed corrupted, that should free some space.
During the tests, we found the old closed indexes seems to not work correctly when they are reopened.
For example for the oldest index apache_logs-2018.07.31:
```
curl -s $ES_SERVER/apache_logs-2018.07.31/_stats\?pretty | jq '._all.primaries.docs'
{
"count": 39984,
"deleted": 0
}
```
A search returns nothing :
```
% curl $ES_SERVER/apache_logs-2018.07.31/_search\?pretty
{
"took" : 0,
"timed_out" : false,
"_shards" : {
"total" : 0,
"successful" : 0,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 0,
"relation" : "eq"
},
"max_score" : 0.0,
"hits" : [ ]
}
}
```
A flush or a merge does not change anything.
The impacted indexes are from 2018-07-31 to 2020-05-11.
[1] T2787#58155