CODEWITHSUNDEEP
cassandraubuntu-14.04datastaxdatastax-enterprise
uh_big_mike_boi
uh_big_mike_boi

Reputation: 3470

Cassandra moving data_file_firectories

Regarding the location of cassandra created data files and system files, I need to move the "commitlog_directory", "data_file_directories" and "saved_caches_directory" which have settings in the "cassandra.yaml" config file. It is currently at the default location "/var/lib/cassandra". The data is only some test data and of course the system generated keyspaces which are 

dse_perf  
dse_system  
OpsCenter  
system  
system_traces

There are also the commitlog and saved_caches.db to move.

I am thinking of moving the keyspace directories with linux shell commands but I'm very unsure if they will become corrupt somehow. There is simply no space in the default drive and we need to move everything to the secondary and tertiary mounted drives.

Right now I'm in the process of moving all the files and resetting the yaml settings.

I have two questions -

  1. Regarding the cassandra.yaml file, are there any other files besides this that are depended upon to have the location of the commitlog_directory and data_file_directories and saved_caches_directory, and their 'wrong location' will cause failure once I move all these files? I am also concerned the files (like the db files) inside the tables themselves have references to their own location and cause failure once they are moved.

  2. If I just move the three settings commitlog_directory and data_file_directories and saved_caches_directory, will dse/cassandra actually create all the system keyspaces (system_traces, dse_perf, system, OpsCenter, dse_system), and the commitlof and the saved_caches.db, and will any other upstream config files be out of sync with that (same as first part of question 1)?

It is a very new installation so re installing would not be the end of the world but I realllly don't want to because we have kerberos and all kinds of other stuff on top of this cluster now.

This OS is ubuntu 14.0.4 and the DSE version is 4.7.

Upvotes: 3

Views: 705

Answers (2)

LHWizard
LHWizard

Reputation: 2379

I just finished doing this. My instances are in AWS EC2 so your process may vary, but in essence:

  1. create a new volume and attach it to the instance. my new device was /dev/xvdg.
  2. create new mount point sudo mkdir /new_data
  3. format the new volume sudo mkfs -t ext4 /dev/xvdg
  4. edit /etc/fstab so that your mount will survive reboots and add this line /dev/xvdg /new_data ext4 defaults,nofail,nobootwait 0 2
  5. mount the new volume sudo mount -a
  6. make the new directories sudo mkdir -p /new_data/lib/cassandra/commitlog
  7. chown the ownership sudo chown -R cassandra:cassandra /new_data/lib/cassandra
  8. change cassandra.yaml to point to the new dirs
  9. drain the node. if you're moving the data dir, copy over the data from the old location to the new location. if you're moving commitlog only, just restart cassandra.

Upvotes: 4

uh_big_mike_boi
uh_big_mike_boi

Reputation: 3470

I was able to move all the files and the commitlog as well. I changed the yaml and pointed it to where I wanted it to go. Remember to run the following command afterward -

chown -R cassandra:cassandra

And voila! Everything is reading/writing as it should. Cassandra is neato.

Upvotes: 1

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