ernado
11 years ago
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Replication |
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=================================== |
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Weed-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 -defaultReplicationType=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 WeedFS 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 |
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