Revision d3b06210 doc/design-partitioned.rst
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Exclusive use of disks |
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``exclusive_storage`` is a configuration flag at node-group and cluster |
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level. When it's enabled, Ganeti will allocate entire disks to |
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instances. Though it's possible to think of ways of doing something |
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similar for other storage back-ends, this design targets only ``plain`` |
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and ``drbd``. The name is generic enough in case the feature will be |
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extended to other back-ends. |
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``exclusive_storage`` is a new node parameter. When it's enabled, Ganeti |
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will allocate entire disks to instances. Though it's possible to think |
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of ways of doing something similar for other storage back-ends, this |
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design targets only ``plain`` and ``drbd``. The name is generic enough |
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in case the feature will be extended to other back-ends. The flag value |
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should be homogeneous within a node-group; ``cluster-verify`` will report |
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any violation of this condition. |
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Ganeti will consider each physical volume in the destination volume |
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group as a host disk (for proper isolation, an administrator should |
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When creating a new disk for an instance, Ganeti will allocate the |
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minimum number of PVs to hold the disk, and those PVs will be excluded |
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from the pool of available PVs by marking them as unallocatable; in this |
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way, PVs won't be shared between instance disks, and any remaining space |
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won't be used by mistake for anything else. The underlying LV will be |
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striped, when striping is allowed by the current configuration. Ganeti |
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will continue to track only the LVs, and query the LVM layer to figure |
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out which PVs are available and how much space is free. |
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from the pool of available PVs for further disk creations. The |
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underlying LV will be striped, when striping is allowed by the current |
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configuration. Ganeti will continue to track only the LVs, and query the |
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LVM layer to figure out which PVs are available and how much space is |
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free. Yet, creation, disk growing, and free-space reporting will ignore |
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any partially allocated PVs, so that PVs won't be shared between |
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instance disks. |
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For compatibility with the DRBD template and to take into account disk |
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variability, Ganeti will always subtract 2% (this will be a parameter) |
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