Issue
ERROR [main] 2017-08-04 13:24:21,949 CassandraDaemon.java:638 - Detected unreadable sstables /opt/cassandra/data/some_key_space/ep_lc_events-adc44160dbe611e6953689bcd3ed73aa/mc-547-big-Summary.db, and many others...
That has happened after I upgraded Cassandra to 3 version and after a while downgraded it to 2nd version.
When I run this command: sudo service cassandra status
I have got such message:
could not access pidfile for Cassandra
In /var/log/cassandra/system.log I have logs which I wrote at the beginning.
PS: let me pay your attention that everything is happening on EC2 Amazon instance.
Solution
Well, I have just upgraded back to 3rd version, used cassandra-unloader to export all data, then downgraded back to 2nd version and used cassandra-loader to import all data. But if you were lucky and had backups and snapshots it would not be an obstacle for you.
PS. Afterwards, I had to run this command nodetool resetlocalschema to reset local schema and resynchronize.
PPS. This you can find how to do that. https://github.com/brianmhess/cassandra-loader
Answered By - AndrewKoropets Answer Checked By - David Marino (WPSolving Volunteer)
