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From rake...@apache.org
Subject [25/50] [abbrv] hadoop git commit: HDFS-11874. [SPS]: Document the SPS feature. Contributed by Uma Maheswara Rao G
Date Wed, 24 Jan 2018 07:32:20 GMT
HDFS-11874. [SPS]: Document the SPS feature. Contributed by Uma Maheswara Rao G

Project: http://git-wip-us.apache.org/repos/asf/hadoop/repo
Commit: http://git-wip-us.apache.org/repos/asf/hadoop/commit/f997f612
Tree: http://git-wip-us.apache.org/repos/asf/hadoop/tree/f997f612
Diff: http://git-wip-us.apache.org/repos/asf/hadoop/diff/f997f612

Branch: refs/heads/HDFS-10285
Commit: f997f612160be4e13b8633517f82c677bd7a566f
Parents: d770a2f
Author: Rakesh Radhakrishnan <rakeshr@apache.org>
Authored: Fri Jul 14 22:36:09 2017 +0530
Committer: Rakesh Radhakrishnan <rakeshr@apache.org>
Committed: Wed Jan 24 11:13:45 2018 +0530

 .../src/site/markdown/ArchivalStorage.md        | 51 ++++++++++++++++++--
 1 file changed, 48 insertions(+), 3 deletions(-)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ArchivalStorage.md b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ArchivalStorage.md
index f1895fc..668bb20 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ArchivalStorage.md
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/ArchivalStorage.md
@@ -95,8 +95,44 @@ The effective storage policy can be retrieved by the "[`storagepolicies
     The default storage type of a datanode storage location will be DISK if it does not have
a storage type tagged explicitly.
-Mover - A New Data Migration Tool
+Storage Policy Based Data Movement
+Setting a new storage policy on already existing file/dir will change the policy in Namespace,
but it will not move the blocks physically across storage medias.
+Following 2 options will allow users to move the blocks based on new policy set. So, once
user change/set to a new policy on file/directory, user should also perform one of the following
options to achieve the desired data movement. Note that both options cannot be allowed to
run simultaneously.
+### <u>S</u>torage <u>P</u>olicy <u>S</u>atisfier (SPS)
+When user changes the storage policy on a file/directory, user can call `HdfsAdmin` API `satisfyStoragePolicy()`
to move the blocks as per the new policy set.
+The SPS daemon thread runs along with namenode and periodically scans for the storage mismatches
between new policy set and the physical blocks placed. This will only track the files/directories
for which user invoked satisfyStoragePolicy. If SPS identifies some blocks to be moved for
a file, then it will schedule block movement tasks to datanodes. A Coordinator DataNode(C-DN)
will track all block movements associated to a file and notify to namenode about movement
success/failure. If there are any failures in movement, the SPS will re-attempt by sending
new block movement task.
+SPS can be activated and deactivated dynamically without restarting the Namenode.
+Detailed design documentation can be found at [Storage Policy Satisfier(SPS) (HDFS-10285)](https://issues.apache.org/jira/browse/HDFS-10285)
+* **Note**: When user invokes `satisfyStoragePolicy()` API on a directory, SPS will consider
the files which are immediate to that directory. Sub-directories won't be considered for satisfying
the policy. Its user responsibility to call this API on directories recursively, to track
all files under the sub tree.
+* HdfsAdmin API :
+        `public void satisfyStoragePolicy(final Path path) throws IOException`
+* Arguments :
+| | |
+|:---- |:---- |
+| `path` | A path which requires blocks storage movement. |
+*   **dfs.storage.policy.satisfier.activate** - Used to activate or deactivate SPS. Configuring
true represents SPS is
+   activated and vice versa.
+*   **dfs.storage.policy.satisfier.recheck.timeout.millis** - A timeout to re-check the processed
block storage movement
+   command results from Co-ordinator Datanode.
+*   **dfs.storage.policy.satisfier.self.retry.timeout.millis** - A timeout to retry if no
block movement results reported from
+   Co-ordinator Datanode in this configured timeout.
+### Mover - A New Data Migration Tool
 A new data migration tool is added for archiving data. The tool is similar to Balancer. It
periodically scans the files in HDFS to check if the block placement satisfies the storage
policy. For the blocks violating the storage policy, it moves the replicas to a different
storage type in order to fulfill the storage policy requirement. Note that it always tries
to move block replicas within the same node whenever possible. If that is not possible (e.g.
when a node doesn’t have the target storage type) then it will copy the block replicas to
another node over the network.
@@ -113,6 +149,10 @@ A new data migration tool is added for archiving data. The tool is similar
to Ba
 Note that, when both -p and -f options are omitted, the default path is the root directory.
+####Administrator notes:
+`StoragePolicySatisfier` and `Mover tool` cannot run simultaneously. If a Mover instance
is already triggered and running, SPS will be deactivated while starting. In that case, administrator
should make sure, Mover execution finished and then activate SPS again. Similarly when SPS
activated already, Mover cannot be run. If administrator is looking to run Mover tool explicitly,
then he/she should make sure to deactivate SPS first and then run Mover. Please look at the
commands section to know how to activate or deactivate SPS dynamically.
 Storage Policy Commands
@@ -171,7 +211,8 @@ Get the storage policy of a file or a directory.
 ### Satisfy Storage Policy
-Schedule blocks to move based on file/directory policy. This command applicable only to the
given path and its immediate children. Sub-directories won't be considered for satisfying
the policy.
+Schedule blocks to move based on file's/directory's current storage policy.
+Note: For directory case, it will consider immediate files under that directory and it will
not consider sub directories recursively.
 * Command:
@@ -191,4 +232,8 @@ Check the running status of Storage Policy Satisfier in namenode. If it
is runni
         hdfs storagepolicies -isSPSRunning
+### Activate or Deactivate SPS without restarting Namenode
+If administrator wants to activate or deactivate SPS feature while Namenode is running, first
he/she needs to update the desired value(true or false) for the configuration item `dfs.storage.policy.satisfier.activate`
in configuration file (`hdfs-site.xml`) and then run the following Namenode reconfig command
++       hdfs dfsadmin -reconfig namenode <host:ipc_port> start

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