Understand More About "disk update time" stat

Hi,

Can anyone please help me to understand about the below 2 KPI’s in detailed.

disk update time => The time required to update data on disk.
disk commit time => The time required to commit data on disk.

I didn’t seen commit option in Couchbase, where this commit came into picture in stats. And in Couchbase there is no update, we have only append even we modify any document.

Thanks,
Vikas