Tsz Wo Nicholas Sze created HDFS-6677:
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Summary: Archival Storage: Change INodeFile and FSImage to support
storage policy
Key: HDFS-6677
URL: https://issues.apache.org/jira/browse/HDFS-6677
Project: Hadoop HDFS
Issue Type: Sub-task
Components: namenode
Reporter: Tsz Wo Nicholas Sze
Assignee: Tsz Wo Nicholas Sze
Policy ID will be stored in INodeFile header with 4 bits which can support 16
different storage policies. The number of bits for replication will be reduced
from 16 bits to 12 bits which is still able to support up to 4095 replicas.
The number of bits for block size remains 48 bits. The memory usage of
INodeFile remains unchanged.
The storage policy IDs assigned to Hot, Warm and Cold policies are respectively
12, 8 and 4. These numbers are chosen with gaps so that future policies can be
added in-between.
We should make a corresponding change in FSImage.
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