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Yongjun Zhang commented on HDFS-9820: ------------------------------------- Thanks [~jingzhao]! Agree. HDFS-4167 also has the restriction that it can only revert back to the most recent snapshot, not any earlier ones, per your comment in the jira: {quote} Note that the snapshot must be the most recent one. We throw exceptions if there are intermediate snapshot. This is the same behavior with ZFS. {quote} > Improve distcp to support efficient restore to an earlier snapshot > ------------------------------------------------------------------ > > Key: HDFS-9820 > URL: https://issues.apache.org/jira/browse/HDFS-9820 > Project: Hadoop HDFS > Issue Type: New Feature > Components: distcp > Reporter: Yongjun Zhang > Assignee: Yongjun Zhang > > HDFS-4167 intends to restore HDFS to the most recent snapshot, and there are > some complexity and challenges. > HDFS-7535 improved distcp performance by avoiding copying files that changed > name since last backup. > On top of HDFS-7535, HDFS-8828 improved distcp performance when copying data > from source to target cluster, by only copying changed files since last > backup. The way it works is use snapshot diff to find out all files changed, > and copy the changed files only. > See > https://blog.cloudera.com/blog/2015/12/distcp-performance-improvements-in-apache-hadoop/ > This jira is to propose a variation of HDFS-8828, to find out the files > changed in target cluster since last snapshot sx, and copy these from the > source target's same snapshot sx, to restore target cluster to sx. > If a file/dir is > - renamed, rename it back > - created in target cluster, delete it > - modified, put it to the copy list > - run distcp with the copy list, copy from the source cluster's corresponding > snapshot > This could be a new command line switch -rdiff in distcp. > HDFS-4167 would still be nice to have. It just seems to me that HDFS-9820 > would hopefully be easier to implement. -- This message was sent by Atlassian JIRA (v6.3.4#6332)