cassandra-people, I'm trying to measure disk usage by cassandra after inserting some columns in order to plan disk sizes and configurations for future deploys.
My approach is very straightforward:
clean_data (stop_cassandra && rm -rf
/var/lib/cassandra/{dara,commitlog,saved_caches}/*)
perform_inserts
measure_disk_usage (nodetool -flush && du -ch /var/lib/cassandra)
There are two types of inserts:
- In a simple column with key, name and value a random string of size 100
- In a super-column with key, super-column-name, name and value a random
string of size 100
But surprisingly when I'm inserting 100 million columns on a simple column
it uses more disk than the same amount in a super-column. How can that be
possible?
For simple column 41984 MB and for super-column 29696, the difference is
more than noticeable!
Somebody told me yesterday that super-columns don't have a per-column
timestamp, but... it in my case, even if every data was in the same
super-column-key it will not explain the difference!
ps: sorry, English is not my first language
results.eps
Description: PostScript document
