HDFS: Under-Replicated Blocks error in HDFS

[#1]

Hi,

Can someone help me on the below issue, please?

Error: Under-Replicated Blocks

19,124 under replicated blocks in the cluster. 38,288 total blocks in the cluster. Percentage under replicated blocks: 49.95%. Critical threshold: 40.00%.

and  Configured Capacity is  40.9 GiB/439.8 GiB

Please find the below report:  sudo -u hdfs hdfs dfsadmin -report

Configured Capacity: 472203141120 (439.77 GB)
Present Capacity: 461408686138 (429.72 GB)
DFS Remaining: 428312064000 (398.90 GB)
DFS Used: 33096622138 (30.82 GB)
DFS Used%: 7.17%
Replicated Blocks:
Under replicated blocks: 19124
Blocks with corrupt replicas: 0
Missing blocks: 0
Missing blocks (with replication factor 1): 0
Low redundancy blocks with highest priority to recover: 19124
Pending deletion blocks: 0
Erasure Coded Block Groups:
Low redundancy block groups: 0
Block groups with corrupt internal blocks: 0
Missing block groups: 0
Low redundancy blocks with highest priority to recover: 0
Pending deletion blocks: 0

-------------------------------------------------
Live datanodes (1):

Name: 11.16.112.253:9866 (cdldtcoevap0001.es.ad.adp.com)
Hostname: cdldtcoevap0001.es.ad.adp.com
Rack: /default
Decommission Status : Normal
Configured Capacity: 472203141120 (439.77 GB)
DFS Used: 33096622138 (30.82 GB)
Non DFS Used: 10794454982 (10.05 GB)
DFS Remaining: 428312064000 (398.90 GB)
DFS Used%: 7.01%
DFS Remaining%: 90.71%
Configured Cache Capacity: 4294967296 (4 GB)
Cache Used: 0 (0 B)
Cache Remaining: 4294967296 (4 GB)
Cache Used%: 0.00%
Cache Remaining%: 100.00%
Xceivers: 2
Last contact: Fri Aug 02 09:08:32 EDT 2019
Last Block Report: Fri Aug 02 08:54:20 EDT 2019

Thanks,

Vijaya

[#2]

Hi Vijaya,

Under-replicated blocks are the blocks which does not meet the target replication factor. HDFS has self healing mechanism wherein it will create new replicas of under-replicated blocks until they meet the target replication. 

if multi node cluster then you can verify if any datanodes are down  Or if it is one node cluster then please ensure replication factor is set to 1. 

Thanks.