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Subject [GitHub] dawidwys commented on a change in pull request #6766: [docs] Improve documentation of savepoints
Date Thu, 27 Sep 2018 11:23:13 GMT
dawidwys commented on a change in pull request #6766: [docs] Improve documentation of savepoints
URL: https://github.com/apache/flink/pull/6766#discussion_r220867491
 
 

 ##########
 File path: docs/ops/state/savepoints.md
 ##########
 @@ -25,17 +25,29 @@ under the License.
 * toc
 {:toc}
 
-## Overview
+## What is a Savepoint? How is a Savepoint different from a Checkpoint?
 
-Savepoints are externally stored self-contained checkpoints that you can use to stop-and-resume
or update your Flink programs. They use Flink's [checkpointing mechanism]({{ site.baseurl
}}/internals/stream_checkpointing.html) to create a (non-incremental) snapshot of the state
of your streaming program and write the checkpoint data and meta data out to an external file
system.
-
-This page covers all steps involved in triggering, restoring, and disposing savepoints.
-For more details on how Flink handles state and failures in general, check out the [State
in Streaming Programs]({{ site.baseurl }}/dev/stream/state/index.html) page.
+A Savepoint is a consistent image of the execution state of a streaming job, created via
Flink's [checkpointing mechanism]({{ site.baseurl }}/internals/stream_checkpointing.html).
You can use Savepoints to stop-and-resume, fork,
+or update your Flink jobs. Savepoints consist of two parts: a directory with (typically large)
binary files on stable storage (e.g. HDFS, S3, ...) and a (relatively small) meta data file.
The files on stable storage represent the net data of the job's execution state
+image. The meta data file of a Savepoint contains (primarily) pointers to all file on stable
storage that are part of the Savepoint, in form of absolute paths.
 
 <div class="alert alert-warning">
 <strong>Attention:</strong> In order to allow upgrades between programs and Flink
versions, it is important to check out the following section about <a href="#assigning-operator-ids">assigning
IDs to your operators</a>.
 </div>
 
+Flink's Savepoints are different from Checkpoints in a similar way that backups are different
from recovery logs in traditional database systems. The primary purpose of Checkpoints is
the provide a recovery mechanism in case of
 
 Review comment:
   is the provide -> is to provide?

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