perfSONAR User Q&A and Other Discussion

[Hyojoon Kim <>]

Hi all, 

We are going to build a new MA (measurement archive) machine (call this 
MA-2), which is going to take over the functionality of our old MA machine 
(call this MA-1). I want to make sure this process goes smoothly, and more 
importantly, without losing historical data. 

To preserve the historical data we have collected so far on MA-1, I am 
thinking to follow these steps:

0. Keep MA-1 running as usual. 
1. On MA-2, stop Cassandra and PostgreSQL service for now. (service cassandra 
stop, service pgsql stop) 
2. Configure all perfSONAR nodes to send measurement data to *both* MA-1 and 
MA-2. 
3. Configure MA-2 so that it's ready to receive measurement data from all 
perfSONAR nodes. However, don’t start Cassandra and PostgreSQL service yet. 
4. On MA-1, stop Cassandra and PostgreSQL service, then copy over 
“/var/lib/cassandra” and “/var/lib/pgsql” to MA-2, same directory location. 
5. When copying is done, start Cassandra and PostgreSQL service on MA-2. 
6. Configure all perfSONAR nodes to stop sending data to MA-1. 
7. Get rid of MA-1. 

Will this generally work? I just want to make sure some step doesn’t 
*overwrite* historical data with new data on MA-2. 

I am also assuming that the time gap when perfSONAR nodes cannot send data to 
either MA-1 and MA-2 (between step 4 and 5 above) is okay as far as it’s not 
too long, because that failed-to-send-data will be backlogged in each node 
for at least some time, without losing that data. Well, some loss of 
measurement data during the migration is relatively tolerable, compared to 
the loss of historical data. 

Any feedback would be helpful! 

Thanks,
Joon