Are there any side effects to turning major compactions off, other than just a 
hit in the read performance?

I was trying to merge a 120 Gig update (modify/insert/delete operations) into a 
2 TB fully compacted Hbase table with 5 region servers using a map reduce job.. 
Each RS was serving around 2000 regions (256 MB max size)... Major compactions 
were turned off before the job started (by setting the compaction period very 
high to around 4 or 5 days)..

As the job was going on, the region servers just shut down after the table 
reached near-100% fragmentation (as shown in the web interface)..  On looking 
at the RS logs, I saw that there were compaction checks for each region which 
obviously didn't clear, and the RS's shut down soon after the checks..  I tried 
restarting the database after killing the map reduce job (still, with major 
compactions turned off).. The RS's shut down soon after booting up..

   Is this expected? Even if the update files (the additional StoreFiles) per 
region get huge, won't the region get split on its own?

Thank you
Vidhya

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