qinyuren created HDFS-16420:
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Summary: ec + balancer may cause missing block
Key: HDFS-16420
URL: https://issues.apache.org/jira/browse/HDFS-16420
Project: Hadoop HDFS
Issue Type: Bug
Reporter: qinyuren
Attachments: image-2022-01-10-17-31-35-910.png,
image-2022-01-10-17-32-56-981.png
We have a similar problem as HDFS-16297 described.
In our cluster, we used ec(6+3) + balancer, and the missing block happened.
We got the block(blk_-9223372036824119008) info from fsck, only 5 live
replications and multiple redundant replications.
blk_-9223372036824119008_220037616 len=133370338 MISSING! Live_repl=5
blk_-9223372036824119007:DatanodeInfoWithStorage,
blk_-9223372036824119002:DatanodeInfoWithStorage,
blk_-9223372036824119001:DatanodeInfoWithStorage,
blk_-9223372036824119000:DatanodeInfoWithStorage,
blk_-9223372036824119004:DatanodeInfoWithStorage,
blk_-9223372036824119004:DatanodeInfoWithStorage,
blk_-9223372036824119004:DatanodeInfoWithStorage,
blk_-9223372036824119004:DatanodeInfoWithStorage,
blk_-9223372036824119004:DatanodeInfoWithStorage,
blk_-9223372036824119004:DatanodeInfoWithStorage
We searched the log from all datanode, and found that the internal blocks of
blk_-9223372036824119008 were deleted almost at the same time.
08:15:58,521 INFO impl.FsDatasetAsyncDiskService
(FsDatasetAsyncDiskService.java:deleteAsync(225)) - Scheduling
blk_-9223372036824119008_220037616 replica FinalizedReplica,
blk_-9223372036824119008_220037616, FINALIZED
08:15:58,550 INFO impl.FsDatasetAsyncDiskService
(FsDatasetAsyncDiskService.java:run(333)) - Deleted
BP-1606066499-xxxx-1606188026755 blk_-9223372036824119008_220037616 URI
file:/data15/hadoop/hdfs/data/current/BP-1606066499-xxxx-1606188026755/current/finalized/subdir19/subdir9/blk_-9223372036824119008
08:16:21,214 INFO impl.FsDatasetAsyncDiskService
(FsDatasetAsyncDiskService.java:run(333)) - Deleted
BP-1606066499-xxxx-1606188026755 blk_-9223372036824119006_220037616 URI
file:/data4/hadoop/hdfs/data/current/BP-1606066499-xxxx-1606188026755/current/finalized/subdir19/subdir9/blk_-9223372036824119006
08:16:55,737 INFO impl.FsDatasetAsyncDiskService
(FsDatasetAsyncDiskService.java:run(333)) - Deleted
BP-1606066499-xxxx-1606188026755 blk_-9223372036824119005_220037616 URI
file:/data2/hadoop/hdfs/data/current/BP-1606066499-xxxx-1606188026755/current/finalized/subdir19/subdir9/blk_-9223372036824119005
The total number of internal blocks deleted during 08:15-08:17 are as follows
internal block delete num
blk_-9223372036824119008 1
blk_-9223372036824119006 1
blk_-9223372036824119005 1
blk_-9223372036824119004 50
blk_-9223372036824119003 1
blk_-9223372036824119000 1
During 08:15 to 08:17, we restarted 2 Datanodes and triggered full block
reporting immediately.
There are 2 questions:
1. Why are there so many replicas of this block?
2. Why delete the internal block with only one copy?
The reasons for the first problem may be as follows:
1. We set the full block report period of some datanodes to 168 hours.
2. We have done a namenode HA operation.
3. After namenode HA, the state of storage became stale, and the state not
change until next full block report.
4. The balancer copied the replica without deleting the replica from source
node, because the source node have the stale storage, and the request was put
into postponedMisreplicatedBlocks.
5. Balancer continues to copy the replica, eventually resulting in multiple
copies of a replica
!image-2022-01-10-17-31-35-910.png!
The set of rescannedMisreplicatedBlocks have so many block to remove.
!image-2022-01-10-17-32-56-981.png!
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