Anu Engineer created HDFS-11922:
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Summary: Ozone: KSM: Garbage collect deleted blocks
Key: HDFS-11922
URL: https://issues.apache.org/jira/browse/HDFS-11922
Project: Hadoop HDFS
Issue Type: Sub-task
Components: ozone
Reporter: Anu Engineer
Priority: Critical
We need to garbage collect deleted blocks from the Datanodes. There are two
cases where we will have orphaned blocks. One is like the classical HDFS, where
someone deletes a key and we need to delete the corresponding blocks.
Another case, is when someone overwrites a key -- an overwrite can be treated
as a delete and a new put -- that means that older blocks need to be GC-ed at
some point of time.
Couple of JIRAs has discussed this in one form or another -- so consolidating
all those discussions in this JIRA.
HDFS-11796 -- needs to fix this issue for some tests to pass
HDFS-11780 -- changed the old overwriting behavior to not supporting this
feature for time being.
HDFS-11920 - Once again runs into this issue when user tries to put an existing
key.
HDFS-11781 - delete key API in KSM only deletes the metadata -- and relies on
GC for Datanodes.
When we solve this issue, we should also consider 2 more aspects.
One, we support versioning in the buckets, tracking which blocks are really
orphaned is something that KSM will do. So delete and overwrite at some point
needs to decide how to handle versioning of buckets.
Two, If a key exists in a closed container, then it is immutable, hence the
strategy of removing the key might be more complex than just talking to an open
container.
cc : [~xyao], [~cheersyang], [~vagarychen], [~msingh], [~yuanbo], [~szetszwo],
[~nandakumar131]
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