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https://issues.apache.org/jira/browse/HDFS-6489?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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stanley shi updated HDFS-6489:
------------------------------
Description:
The current implementation of the Datanode will increase the DFS used space on
each block write operation. This is correct in most scenario (create new file),
but sometimes it will behave in-correct(append small data to a large block).
For example, I have a file with only one block(say, 60M). Then I try to append
to it very frequently but each time I append only 10 bytes;
Then on each append, dfs used will be increased with the length of the
block(60M), not teh actual data length(10bytes).
Consider in a scenario I use many clients to append concurrently to a large
number of files (1000+), assume the block size is 32M (half of the default
value), then the dfs used will be increased 1000*32M = 32G on each append to
the files; but actually I only write 10K bytes; this will cause the datanode to
report in-sufficient disk space on data write.
{quote}2014-06-04 15:27:34,719 INFO
org.apache.hadoop.hdfs.server.datanode.DataNode: opWriteBlock
BP-1649188734-10.37.7.142-1398844098971:blk_1073742834_45306 received exception
org.apache.hadoop.util.DiskChecker$DiskOutOfSpaceException: Insufficient space
for appending to FinalizedReplica, blk_1073742834_45306, FINALIZED{quote}
But the actual disk usage:
{quote}
[root@hdsh143 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 16G 2.9G 13G 20% /
tmpfs 1.9G 72K 1.9G 1% /dev/shm
/dev/sda1 97M 32M 61M 35% /boot
{quote}
was:
The current implementation of the Datanode will increase the DFS used space on
each block write operation. This is correct in most scenario (create new file),
but sometimes it will behave in-correct(append small data to a large block).
For example, I have a file with only one block(say, 60M). Then I try to append
to it very frequently but each time I append only 10 bytes;
Then on each append, dfs used will be increased with the length of the
block(60M), not teh actual data length(10bytes).
Consider in a scenario I use many clients to append concurrently to a large
number of files (1000+), assume the block size is 32M (half of the default
value), then the dfs used will be increased 1000*32M = 32G on each append to
the files; but actually I only write 10K bytes; this will cause the datanode to
report in-sufficient disk space on data write.
{quote}2014-06-04 15:27:34,719 INFO
org.apache.hadoop.hdfs.server.datanode.DataNode: opWriteBlock
BP-1649188734-10.37.7.142-1398844098971:blk_1073742834_45306 received exception
org.apache.hadoop.util.DiskChecker$DiskOutOfSpaceException: Insufficient space
for appending to FinalizedReplica, blk_1073742834_45306, FINALIZED{quote}
> DFS Used space is not correct computed on frequent append operations
> --------------------------------------------------------------------
>
> Key: HDFS-6489
> URL: https://issues.apache.org/jira/browse/HDFS-6489
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Affects Versions: 2.2.0
> Reporter: stanley shi
>
> The current implementation of the Datanode will increase the DFS used space
> on each block write operation. This is correct in most scenario (create new
> file), but sometimes it will behave in-correct(append small data to a large
> block).
> For example, I have a file with only one block(say, 60M). Then I try to
> append to it very frequently but each time I append only 10 bytes;
> Then on each append, dfs used will be increased with the length of the
> block(60M), not teh actual data length(10bytes).
> Consider in a scenario I use many clients to append concurrently to a large
> number of files (1000+), assume the block size is 32M (half of the default
> value), then the dfs used will be increased 1000*32M = 32G on each append to
> the files; but actually I only write 10K bytes; this will cause the datanode
> to report in-sufficient disk space on data write.
> {quote}2014-06-04 15:27:34,719 INFO
> org.apache.hadoop.hdfs.server.datanode.DataNode: opWriteBlock
> BP-1649188734-10.37.7.142-1398844098971:blk_1073742834_45306 received
> exception org.apache.hadoop.util.DiskChecker$DiskOutOfSpaceException:
> Insufficient space for appending to FinalizedReplica, blk_1073742834_45306,
> FINALIZED{quote}
> But the actual disk usage:
> {quote}
> [root@hdsh143 ~]# df -h
> Filesystem Size Used Avail Use% Mounted on
> /dev/sda3 16G 2.9G 13G 20% /
> tmpfs 1.9G 72K 1.9G 1% /dev/shm
> /dev/sda1 97M 32M 61M 35% /boot
> {quote}
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