Couchbase use too much memory when insert data

Hi every one, I’m an couchbase beginner.
Today, I tried to import data into couchbase using PHP. But I think It’s use too much Memory( extremely larger than Data Size). When I insert 1GB data, it take more than 20GB RAM. This only occurs when data is inserting, after that, RAM usage reduce.
When I tried this PHP code, but insert into MySQL not Couchbase, it dont use as much as memory like that.
I used Ubuntu 14.04.
Pls tell me why this happen :slight_smile: thank you

I’ve replied to this as a linked topic, as it was off topic for Couchbase Server’s category.