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HDFS-7147. Update archival storage user documentation. Contributed by Tsz Wo Nicholas Sze.

This commit is contained in:
Haohui Mai 2014-11-03 15:10:22 -08:00
parent f2ef8c7b48
commit e94a044d18
5 changed files with 74 additions and 254 deletions
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3
hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
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@ -711,6 +711,9 @@ Release 2.6.0 - UNRELEASED
HDFS-7291. Persist in-memory replicas with appropriate unbuffered copy API
on POSIX and Windows. (Xiaoyu Yao via cnauroth)
HDFS-7147. Update archival storage user documentation.
(Tsz Wo Nicholas Sze via wheat9)
BREAKDOWN OF HDFS-6134 AND HADOOP-10150 SUBTASKS AND RELATED JIRAS
HDFS-6387. HDFS CLI admin tool for creating & deleting an

6
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockStoragePolicySuite.java
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@ -18,7 +18,9 @@
package org.apache.hadoop.hdfs.server.blockmanagement;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import org.apache.hadoop.fs.XAttr;
import org.apache.hadoop.hdfs.StorageType;
import org.apache.hadoop.hdfs.XAttrHelper;
@ -104,9 +106,11 @@ public class BlockStoragePolicySuite {
}
public BlockStoragePolicy getPolicy(String policyName) {
Preconditions.checkNotNull(policyName);
if (policies != null) {
for (BlockStoragePolicy policy : policies) {
if (policy != null && policy.getName().equals(policyName)) {
if (policy != null && policy.getName().equalsIgnoreCase(policyName)) {
return policy;
}
}

118
hadoop-hdfs-project/hadoop-hdfs/src/main/resources/blockStoragePolicy-default.xml
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@ -1,118 +0,0 @@
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<!-- Do not modify this file directly. Instead, copy entries that you wish -->
<!-- to modify from this file into blockStoragePolicy-site.xml and change -->
<!-- there. If blockStoragePolicy-site.xml does not exist, create it. -->
<configuration>
<property>
<name>dfs.block.storage.policies</name>
<value>HOT:12, WARM:8, COLD:4</value>
<description>
A list of block storage policy names and IDs. The syntax is
NAME_1:ID_1, NAME_2:ID_2, ..., NAME_n:ID_n
where ID is an integer in the range [1,15] and NAME is case insensitive.
The first element is the default policy. Empty list is not allowed.
</description>
</property>
<!-- Block Storage Policy HOT:12 -->
<property>
<name>dfs.block.storage.policy.12</name>
<value>DISK</value>
<description>
A list of storage types for storing the block replicas such as
STORAGE_TYPE_1, STORAGE_TYPE_2, ..., STORAGE_TYPE_n
When creating a block, the i-th replica is stored using i-th storage type
for i less than or equal to n, and
the j-th replica is stored using n-th storage type for j greater than n.
Empty list is not allowed.
Examples:
DISK : all replicas stored using DISK.
DISK, ARCHIVE : the first replica is stored using DISK and all the
remaining replicas are stored using ARCHIVE.
</description>
</property>
<property>
<name>dfs.block.storage.policy.creation-fallback.12</name>
<value></value>
<description>
A list of storage types for creation fallback storage.
STORAGE_TYPE_1, STORAGE_TYPE_2, ..., STORAGE_TYPE_n
When creating a block, if a particular storage type specified in the policy
is unavailable, the fallback STORAGE_TYPE_1 is used. Further, if
STORAGE_TYPE_i is also unavailable, the fallback STORAGE_TYPE_(i+1) is used.
In case that all fallback storages are unavailabe, the block will be created
with number of replicas less than the specified replication factor.
An empty list indicates that there is no fallback storage.
</description>
</property>
<property>
<name>dfs.block.storage.policy.replication-fallback.12</name>
<value>ARCHIVE</value>
<description>
Similar to dfs.block.storage.policy.creation-fallback.x but for replication.
</description>
</property>
<!-- Block Storage Policy WARM:8 -->
<property>
<name>dfs.block.storage.policy.8</name>
<value>DISK, ARCHIVE</value>
</property>
<property>
<name>dfs.block.storage.policy.creation-fallback.8</name>
<value>DISK, ARCHIVE</value>
</property>
<property>
<name>dfs.block.storage.policy.replication-fallback.8</name>
<value>DISK, ARCHIVE</value>
</property>
<!-- Block Storage Policy COLD:4 -->
<property>
<name>dfs.block.storage.policy.4</name>
<value>ARCHIVE</value>
</property>
<property>
<name>dfs.block.storage.policy.creation-fallback.4</name>
<value></value>
</property>
<property>
<name>dfs.block.storage.policy.replication-fallback.4</name>
<value></value>
</property>
</configuration>

199
hadoop-hdfs-project/hadoop-hdfs/src/site/apt/ArchivalStorage.apt.vm
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@ -11,12 +11,12 @@
~~ limitations under the License. See accompanying LICENSE file.
---
HDFS Archival Storage
Archival Storage, SSD & Memory
---
---
${maven.build.timestamp}
HDFS Archival Storage
Archival Storage, SSD & Memory
%{toc|section=1|fromDepth=0}
@ -29,9 +29,13 @@ HDFS Archival Storage
Adding more nodes to the cold storage can grow the storage independent of the compute capacity
in the cluster.
The frameworks provided by Heterogeneous Storage and Archival Storage generalizes the HDFS architecture
to include other kinds of storage media including <SSD> and <memory>.
Users may choose to store their data in SSD or memory for a better performance.
* {Storage Types and Storage Policies}
** {Storage Types: DISK, SSD and ARCHIVE}
** {Storage Types: ARCHIVE, DISK, SSD and RAM_DISK}
The first phase of
{{{https://issues.apache.org/jira/browse/HDFS-2832}Heterogeneous Storage (HDFS-2832)}}
@ -45,7 +49,9 @@ HDFS Archival Storage
which has high storage density (petabyte of storage) but little compute power,
is added for supporting archival storage.
** {Storage Policies: Hot, Warm and Cold}
Another new storage type <RAM_DISK> is added for supporting writing single replica files in memory.
** {Storage Policies: Hot, Warm, Cold, All_SSD, One_SSD and Lazy_Persist}
A new concept of storage policies is introduced in order to allow files to be stored
in different storage types according to the storage policy.
@ -65,6 +71,14 @@ HDFS Archival Storage
When a block is warm, some of its replicas are stored in DISK
and the remaining replicas are stored in ARCHIVE.
* <<All_SSD>> - for storing all replicas in SSD.
* <<One_SSD>> - for storing one of the replicas in SSD.
The remaining replicas are stored in DISK.
* <<Lazy_Persist>> - for writing blocks with single replica in memory.
The replica is first written in RAM_DISK and then it is lazily persisted in DISK.
[]
More formally, a storage policy consists of the following fields:
@ -89,149 +103,54 @@ HDFS Archival Storage
The following is a typical storage policy table.
*--------+---------------+-------------------------+-----------------------+-----------------------+
| <<Policy>> | <<Policy>>| <<Block Placement>> | <<Fallback storages>> | <<Fallback storages>> |
| <<ID>> | <<Name>> | <<(n\ replicas)>> | <<for creation>> | <<for replication>> |
*--------+---------------+-------------------------+-----------------------+-----------------------+
| 12 | Hot (default) | DISK: <n> | \<none\> | ARCHIVE |
*--------+---------------+-------------------------+-----------------------+-----------------------+
| 8 | Warm | DISK: 1, ARCHIVE: <n>-1 | ARCHIVE, DISK | ARCHIVE, DISK |
*--------+---------------+-------------------------+-----------------------+-----------------------+
| 4 | Cold | ARCHIVE: <n> | \<none\> | \<none\> |
*--------+---------------+-------------------------+-----------------------+-----------------------+
*--------+---------------+--------------------------+-----------------------+-----------------------+
| <<Policy>> | <<Policy>>| <<Block Placement>> | <<Fallback storages>> | <<Fallback storages>> |
| <<ID>> | <<Name>> | <<(n\ replicas)>> | <<for creation>> | <<for replication>> |
*--------+---------------+--------------------------+-----------------------+-----------------------+
| 15 | Lasy_Persist | RAM_DISK: 1, DISK: <n>-1 | DISK | DISK |
*--------+---------------+--------------------------+-----------------------+-----------------------+
| 12 | All_SSD | SSD: <n> | DISK | DISK |
*--------+---------------+--------------------------+-----------------------+-----------------------+
| 10 | One_SSD | SSD: 1, DISK: <n>-1 | SSD, DISK | SSD, DISK |
*--------+---------------+--------------------------+-----------------------+-----------------------+
| 7 | Hot (default) | DISK: <n> | \<none\> | ARCHIVE |
*--------+---------------+--------------------------+-----------------------+-----------------------+
| 5 | Warm | DISK: 1, ARCHIVE: <n>-1 | ARCHIVE, DISK | ARCHIVE, DISK |
*--------+---------------+--------------------------+-----------------------+-----------------------+
| 2 | Cold | ARCHIVE: <n> | \<none\> | \<none\> |
*--------+---------------+--------------------------+-----------------------+-----------------------+
Note that cluster administrators may change the storage policy table
according to the characteristic of the cluster.
For example, in order to prevent losing archival data,
administrators may want to use DISK as fallback storage for replication in the Cold policy.
A drawback of such setting is that the DISK storages could be filled up with archival data.
As a result, the entire cluster may become full and cannot serve hot data anymore.
Note that the Lasy_Persist policy is useful only for single replica blocks.
For blocks with more than one replicas, all the replicas will be written to DISK
since writing only one of the replicas to RAM_DISK does not improve the overall performance.
** {Configurations}
** {Storage Policy Resolution}
*** {Setting The List of All Storage Policies}
When a file or directory is created, its storage policy is <unspecified>.
The storage policy can be specified using
the "<<<{{{Set Storage Policy}dfsadmin -setStoragePolicy}}>>>" command.
The effective storage policy of a file or directory is resolved by the following rules.
* <<dfs.block.storage.policies>>
- a list of block storage policy names and IDs.
The syntax is
[[1]] If the file or directory is specificed with a storage policy, return it.
NAME_1:ID_1, NAME_2:ID_2, ..., NAME_<n>:ID_<n>
where ID is an integer in the closed range [1,15] and NAME is case insensitive.
The first element is the <default policy>. Empty list is not allowed.
The default value is shown below.
+------------------------------------------+
<property>
<name>dfs.block.storage.policies</name>
<value>HOT:12, WARM:8, COLD:4</value>
</property>
+------------------------------------------+
[[2]] For an unspecified file or directory,
if it is the root directory, return the <default storage policy>.
Otherwise, return its parent's effective storage policy.
[]
*** {Setting Storage Policy Details}
The effective storage policy can be retrieved by
the "<<<{{{Set Storage Policy}dfsadmin -getStoragePolicy}}>>>" command.
The following configuration properties are for setting the details of each storage policy,
where <<<\<ID\>>>> is the actual policy ID.
* <<dfs.block.storage.policy.\<ID\>>>
- a list of storage types for storing the block replicas.
The syntax is
** {Configuration}
STORAGE_TYPE_1, STORAGE_TYPE_2, ..., STORAGE_TYPE_<n>
When creating a block, the <i>-th replica is stored using <i>-th storage type
for <i> less than or equal to <n>, and
the <j>-th replica is stored using <n>-th storage type for <j> greater than <n>.
Empty list is not allowed.
Examples:
+------------------------------------------+
DISK : all replicas stored using DISK.
DISK, ARCHIVE : the first replica is stored using DISK and all the
remaining replicas are stored using ARCHIVE.
+------------------------------------------+
* <<dfs.block.storage.policy.creation-fallback.\<ID\>>>
- a list of storage types for creation fallback storage.
The syntax is
STORAGE_TYPE_1, STORAGE_TYPE_2, ..., STORAGE_TYPE_n
When creating a block, if a particular storage type specified in the policy
is unavailable, the fallback STORAGE_TYPE_1 is used. Further, if
STORAGE_TYPE_<i> is also unavailable, the fallback STORAGE_TYPE_<(i+1)> is used.
In case all fallback storages are unavailable, the block will be created
with number of replicas less than the specified replication factor.
An empty list indicates that there is no fallback storage.
* <<dfs.block.storage.policy.replication-fallback.\<ID\>>>
- a list of storage types for replication fallback storage.
The usage of this configuration property is similar to
<<<dfs.block.storage.policy.creation-fallback.\<ID\>>>>
except that it takes effect on replication but not block creation.
* <<dfs.storage.policy.enabled>>
- for enabling/disabling the storage policy feature.
The default value is <<<true>>>.
[]
The following are the default configuration values for Hot, Warm and Cold storage policies.
* Block Storage Policy <<HOT:12>>
+------------------------------------------+
<property>
<name>dfs.block.storage.policy.12</name>
<value>DISK</value>
</property>
<property>
<name>dfs.block.storage.policy.creation-fallback.12</name>
<value></value>
</property>
<property>
<name>dfs.block.storage.policy.replication-fallback.12</name>
<value>ARCHIVE</value>
</property>
+------------------------------------------+
* Block Storage Policy <<WARM:8>>
+------------------------------------------+
<property>
<name>dfs.block.storage.policy.8</name>
<value>DISK, ARCHIVE</value>
</property>
<property>
<name>dfs.block.storage.policy.creation-fallback.8</name>
<value>DISK, ARCHIVE</value>
</property>
<property>
<name>dfs.block.storage.policy.replication-fallback.8</name>
<value>DISK, ARCHIVE</value>
</property>
+------------------------------------------+
* Block Storage Policy <<COLD:4>>
+------------------------------------------+
<property>
<name>dfs.block.storage.policy.4</name>
<value>ARCHIVE</value>
</property>
<property>
<name>dfs.block.storage.policy.creation-fallback.4</name>
<value></value>
</property>
<property>
<name>dfs.block.storage.policy.replication-fallback.4</name>
<value></value>
</property>
+------------------------------------------+
[]
* {Mover - A New Data Migration Tool}
@ -261,7 +180,19 @@ hdfs mover [-p <files/dirs> | -f <local file name>]
[]
* {<<<DFSAdmin>>> Commands}
* {Storage Policy Commands}
** {List Storage Policies}
List out all the storage policies.
* Command:
+------------------------------------------+
hdfs storagepolicies
+------------------------------------------+
* Arguments: none.
** {Set Storage Policy}

2
hadoop-project/src/site/site.xml
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@ -93,7 +93,7 @@
<item name="Extended Attributes" href="hadoop-project-dist/hadoop-hdfs/ExtendedAttributes.html"/>
<item name="Transparent Encryption" href="hadoop-project-dist/hadoop-hdfs/TransparentEncryption.html"/>
<item name="HDFS Support for Multihoming" href="hadoop-project-dist/hadoop-hdfs/HdfsMultihoming.html"/>
<item name="Archival Storage" href="hadoop-project-dist/hadoop-hdfs/ArchivalStorage.html"/>
<item name="Archival Storage, SSD &amp; Memory" href="hadoop-project-dist/hadoop-hdfs/ArchivalStorage.html"/>
</menu>
<menu name="MapReduce" inherit="top">