>>However, failure to match the checksum doesn't count as a failed copy, but as an attempt in a different retry mechanism.
After specified number of retries(distcp.file.retries is the config property, with a default value of 3 => by default, 2 more times copy of file is tried in case of checksum mismatch), it is considered as a failure.
>>Are invalid/corrupt copies more common than other failures that throw exceptions (e.g. (re)moved source files, IOExceptions, etc.)?
Am not sure. But this feature would give more confidence to users about copy done by distcp.
>> as long as it's been tested then that's OK.
Yes. It is tested with different cases.