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98 lines
3.9 KiB
ReStructuredText
98 lines
3.9 KiB
ReStructuredText
Replication
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===================================
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Seaweed-FS can support replication. The replication is implemented not on file level, but on volume level.
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How to use
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###################################
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Basically, the way it works is:
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1. start weed master, and optionally specify the default replication type
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.. code-block:: bash
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./weed master -defaultReplication=001
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2. start volume servers as this:
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.. code-block:: bash
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./weed volume -port=8081 -dir=/tmp/1 -max=100
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./weed volume -port=8082 -dir=/tmp/2 -max=100
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./weed volume -port=8083 -dir=/tmp/3 -max=100
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Submitting, Reading, Deleting files has the same steps.
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The meaning of replication type
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###################################
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*Note: This subject to change.*
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+-----+---------------------------------------------------------------------------+
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|000 |no replication, just one copy |
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+-----+---------------------------------------------------------------------------+
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|001 |replicate once on the same rack |
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+-----+---------------------------------------------------------------------------+
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|010 |replicate once on a different rack in the same data center |
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+-----+---------------------------------------------------------------------------+
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|100 |replicate once on a different data center |
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+-----+---------------------------------------------------------------------------+
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|200 |replicate twice on two other different data center |
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+-----+---------------------------------------------------------------------------+
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|110 |replicate once on a different rack, and once on a different data center |
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+-----+---------------------------------------------------------------------------+
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|... |... |
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+-----+---------------------------------------------------------------------------+
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So if the replication type is xyz
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+-------+--------------------------------------------------------+
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|**x** |number of replica in other data centers |
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+-------+--------------------------------------------------------+
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|**y** |number of replica in other racks in the same data center|
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+-------+--------------------------------------------------------+
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|**z** |number of replica in other servers in the same rack |
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+-------+--------------------------------------------------------+
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x,y,z each can be 0, 1, or 2. So there are 9 possible replication types, and can be easily extended.
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Each replication type will physically create x+y+z+1 copies of volume data files.
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Example topology configuration
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###################################
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The Seaweed-FS master server tries to read the default topology configuration file are read from /etc/weedfs/weedfs.conf, if it exists. The topology setting to configure data center and racks file format is as this.
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.. code-block:: xml
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<Configuration>
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<Topology>
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<DataCenter name="dc1">
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<Rack name="rack1">
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<Ip>192.168.1.1</Ip>
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</Rack>
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</DataCenter>
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<DataCenter name="dc2">
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<Rack name="rack1">
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<Ip>192.168.1.2</Ip>
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</Rack>
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<Rack name="rack2">
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<Ip>192.168.1.3</Ip>
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<Ip>192.168.1.4</Ip>
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</Rack>
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</DataCenter>
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</Topology>
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</Configuration>
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Allocate File Key on specific data center
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Volume servers can start with a specific data center name.
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.. code-block:: bash
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weed volume -dir=/tmp/1 -port=8080 -dataCenter=dc1
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weed volume -dir=/tmp/2 -port=8081 -dataCenter=dc2
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Or the master server can determine the data center via volume server's IP address and settings in weed.conf file.
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Now when requesting a file key, an optional "dataCenter" parameter can limit the assigned volume to the specific data center. For example, this specify
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.. code-block:: bash
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http://localhost:9333/dir/assign?dataCenter=dc1 |