Apache Accumulo is migrating from JIRA to GitHub issues. The migration is starting with an initial plan, but it may change as the community uses it. For a description of the initial operating plan see the issues section of How to Contribute and the triaging issues section of Making a Release.
Doing routine activities in less time is one motivation for the migration. Below are some examples.
There is no plan to migrate all existing issues in JIRA. The plan is to only migrate issues that someone is interested in or are actively being worked. Migration is done by linking the JIRA and GitHub issues to each other and then closing the JIRA issue. No new issues should be opened in JIRA. JIRA will eventually be transitioned to a read only state.