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42 lines
2.0 KiB
42 lines
2.0 KiB
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kernel data structure for DRBD-9 |
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This describes the in kernel data structure for DRBD-9. Starting with |
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Linux v3.14 we are reorganizing DRBD to use this data structure. |
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Basic Data Structure |
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==================== |
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A node has a number of DRBD resources. Each such resource has a number of |
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devices (aka volumes) and connections to other nodes ("peer nodes"). Each DRBD |
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device is represented by a block device locally. |
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The DRBD objects are interconnected to form a matrix as depicted below; a |
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drbd_peer_device object sits at each intersection between a drbd_device and a |
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drbd_connection:: |
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/--------------+---------------+.....+---------------\ |
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| resource | device | | device | |
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+--------------+---------------+.....+---------------+ |
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| connection | peer_device | | peer_device | |
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+--------------+---------------+.....+---------------+ |
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: : : : : |
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: : : : : |
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+--------------+---------------+.....+---------------+ |
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| connection | peer_device | | peer_device | |
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\--------------+---------------+.....+---------------/ |
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In this table, horizontally, devices can be accessed from resources by their |
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volume number. Likewise, peer_devices can be accessed from connections by |
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their volume number. Objects in the vertical direction are connected by double |
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linked lists. There are back pointers from peer_devices to their connections a |
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devices, and from connections and devices to their resource. |
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All resources are in the drbd_resources double-linked list. In addition, all |
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devices can be accessed by their minor device number via the drbd_devices idr. |
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The drbd_resource, drbd_connection, and drbd_device objects are reference |
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counted. The peer_device objects only serve to establish the links between |
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devices and connections; their lifetime is determined by the lifetime of the |
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device and connection which they reference.
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