I filed https://issues.apache.org/jira/browse/HADOOP-12326 to do that, you can take a look at the patch. Your understanding is correct: md5 of crc in each block, then md5 of those block md5s.
On Sun, Aug 9, 2015 at 7:35 AM Shashi Vishwakarma <[email protected]> wrote: > Hi Gera, > > Thanks for your input. I have fairly large amount of data and if I go by > -cat option followed by md5sum calculation then it will become time > consuming process. > > I could understand from the code that hadoop checksum is nothing but MD5 > of MD5 of CRC32C and then returning output.I would be more curious to know > if in case I have to create checksum manually that hadoop is doing > internally, then how do I do that? > > Is there any document or link available which can explain that how this > checksum calculation works behind the scene? > > Thanks > Shashi > > On Sat, Aug 8, 2015 at 8:00 AM, Gera Shegalov <[email protected]> wrote: > >> The fs checksum output has more info like bytes per CRC, CRC per block. >> See e.g.: >> https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/MD5MD5CRC32FileChecksum.java >> >> In order to avoid dealing with different formatting or byte order you >> could use md5sum for the remote file as well if the file is reasonably small >> >> hadoop fs -cat /abc.txt | md5sum >> >> On Fri, Aug 7, 2015 at 3:35 AM Shashi Vishwakarma < >> [email protected]> wrote: >> >>> Hi >>> >>> I have a small confusion regarding checksum verification.Lets say , i >>> have a file abc.txt and I transferred this file to hdfs. How do I ensure >>> about data integrity? >>> >>> I followed below steps to check that file is correctly transferred. >>> >>> *On Local File System:* >>> >>> md5sum abc.txt >>> >>> 276fb620d097728ba1983928935d6121 TestFile >>> >>> *On Hadoop Cluster :* >>> >>> hadoop fs -checksum /abc.txt >>> >>> /abc.txt MD5-of-0MD5-of-512CRC32C >>> 000002000000000000000000911156a9cf0d906c56db7c8141320df0 >>> >>> Both output looks different to me. Let me know if I am doing anything >>> wrong. >>> >>> How do I verify if my file is transferred properly into HDFS? >>> >>> Thanks >>> Shashi >>> >> >
