On a cluster running CDH 5.0 or above, you use the hadoop fs –put command to write a 300MB
file into a previously empty directory using an HDFS block size of 64 MB. Just after this command
has finished writing 200 MB of this file, what would another use see when they look in directory?
A.
The directory will appear to be empty until the entire file write is completed on the cluster
B.
They will see the file with a ._COPYING_ extension on its name. If they view the file, they will
see contents of the file up to the last completed block (as each 64MB block is written, that block
becomes available)
C.
They will see the file with a ._COPYING_ extension on its name. If they attempt to view the file,
they will get a ConcurrentFileAccessException until the entire file write is completed on the cluster
D.
They will see the file with its original name. If they attempt to view the file, they will get a
ConcurrentFileAccessException until the entire file write is completed on the cluster
correct answer is B ….
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B
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The answer is D, we tried it.
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B is correct. you can view data in file upto last completed block.
[hduser@cdh-master ~]$ hadoop fs -cat /DVB_Test/VL.txt._COPYING_ | more
15/09/17 14:09:55 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform… using builtin-java classes where applicable
total 104
drwxr-xr-x 2 root root 4096 Sep 23 2011 srv
drwxr-xr-x 2 root root 4096 Sep 23 2011 selinux
drwxr-xr-x 2 root root 4096 Sep 23 2011 opt
drwxr-xr-x 2 root root 4096 Sep 23 2011 mnt
drwxr-xr-x 2 root root 4096 Sep 23 2011 media
drwxr-xr-x 2 root root 4096 Oct 17 2014 cgroup
drwx—— 2 root root 16384 Jul 6 15:40 lost+found
drwxr-xr-x 13 root root 4096 Jul 6 15:43 usr
dr-xr-xr-x 8 root root 4096 Jul 6 15:45 lib
dr-xr-xr-x 2 root root 4096 Jul 6 15:45 bin
drwxr-xr-x 18 root root 4096 Jul 6 15:46 var
dr-xr-xr-x 2 root root 4096 Jul 6 15:47 sbin
dr-xr-xr-x 4 root root 4096 Jul 6 15:47 boot
dr-xr-xr-x 124 root root 0 Jul 18 19:51 proc
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B
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B
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D
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