MapR-DB Frequently Asked Questions

Document created by aalvarez on Jan 31, 2017Last modified by aalvarez on Jun 7, 2017
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  • Getting Started


What’s the Difference Between the Logical and Physical Size of a Table? Are They Similar or Different?  

Would You Suggest a Sample Test Plan for MapR-DB Table Replication? 

Why Doesn’t MapR-DB Allow Co-Processors Such As HBase? 

What is a Tablet? 

When Are Tables Split? At How Many MBs or GBs? 

Why Does the maprcli table info Command Return a Row Count Different from the Count in the HBase Shell?

What is the MapR-DB Log File? Where Does It Live? 

How Many Tables Can a Cluster Handle? What’s the Smallest Table I Can Configure?   

What Happens When a Tablet is Split or Merged in MapR-DB? 

What happens behind the scenes on a MapRDB query? 

How Does MapR-DB Compare to Cassandra, MongoDB, and other NoSQL Databases?


  • Configuration

Unable to increase threads in MapRDB (Current value is 10) 

What are the Replication Topology Restrictions? 

Configuring batch size for AsyncHbase puts to Maprdb 

What Happens If the Gateway Fails After a Synchronous Write is Acknowledged? 

Are Gateway Nodes Licensed? 

What Are the Implications of All Gateways Being Down? 

How Do MapR-DB/MapR-Streams Handle Errors In Situations Where the Gateways Are Up But the Replication Cannot Succeed? 

When I Change the Gateway Configuration on the src Cluster, It Doesn’t Seem to Take Effect for Quite Some Time. Why? 

With Respect to Caching, Does the Thrift Server Act as An Ordinary MapR-DB Client? What Type of Cache Does It Use? 

How Do MapR-DB/MapR-Streams Discover Gateways?  How Do They Update the Replication Gateway List? 

I’ve Set the TTL Such That Lots of Data Should Have Been Deleted From My Table. The Table Size is Not Shrinking. Why?  

What Value Is Used Against a Volume’s Quota? Is it the Total Physical Size or the Total Logical Size? 

Does MapR-DB Perform Load Throttling? 

Can Disable/Enable MapR-DB with Using -noDB or -M7. What Does This Do? 

Why Should I Limit the Number Of Tables In One Volume? 

What Does the table replica autosetup Command Do? 



Is There a Limit On the Number of Tables in a Replication Chain? 

Is There a Limit On The Number of Replication Gateways In a Cluster? 

Is There a Limit On the Number of Replicas for a Table? 

Is There a Limit on the Number of Tables That Can Be Replicated? 

What’s the Difference Between Asynchronous and Synchronous Replication? 

How Does MapR-DB/MapR-Streams Handle Replication Gateway Failures? 


  • Security

Collecting MaprDB Metrics 


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