Causes of Stragglers nternal factors External factors resource capacity of worker resource competition due to nodes is heterogeneous Co-hosted applications resource competition due to v input data skew other MapReduce tasks running on the same worker v remote input or output node source is too slow hardware faultCauses of Stragglers Internal factors External factors ✓ resource capacity of worker nodes is heterogeneous ✓ resource competition due to other MapReduce tasks running on the same worker node ✓ resource competition due to co-hosted applications ✓ input data skew ✓ remote input or output source is too slow ✓ hardware faulty