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src/docs/user/cluster/cluster_repositories.diviner
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| this process. For example, loading the most recent backup snapshot onto the new | this process. For example, loading the most recent backup snapshot onto the new | ||||
| device will substantially reduce the amount of data that needs to be | device will substantially reduce the amount of data that needs to be | ||||
| synchronized. | synchronized. | ||||
| Contracting a Cluster | Contracting a Cluster | ||||
| ===================== | ===================== | ||||
| To reduce the size of an existing cluster, follow these general steps: | If you want to remove working devices from a cluster (for example, to take | ||||
| hosts down for maintenance), first do this for each device: | |||||
| - Disable the bindings from the service to the dead device in Almanac. | - Change the `writable` property on the bindings to "Prevent Writes". | ||||
| - Wait a few moments until the cluster synchronizes (see | |||||
| "Monitoring Services" below). | |||||
| This will ensure that the device you're about to remove is not the only cluster | |||||
| leader, even if the cluster is receiving a high write volume. You can skip this | |||||
| step if the device isn't working property to start with. | |||||
| Once you've stopped writes and waited for synchronization (or if the hosts are | |||||
| not working in the first place) do this for each device: | |||||
| - Disable the bindings from the service to the device in Almanac. | |||||
| If you are removing a device because it failed abruptly (or removing several | If you are removing a device because it failed abruptly (or removing several | ||||
| devices at once) it is possible that some repositories will have lost all their | devices at once; or you skip the "Prevent Writes" step), it is possible that | ||||
| leaders. See "Loss of Leaders" below to understand and resolve this. | some repositories will have lost all their leaders. See "Loss of Leaders" below | ||||
| to understand and resolve this. | |||||
| If you want to put the hosts back in service later: | |||||
| - Enable the bindings again. | |||||
| - Change `writable` back to "Allow Writes". | |||||
| This will restore the cluster to the original state. | |||||
| Monitoring Services | Monitoring Services | ||||
| =================== | =================== | ||||
| You can get an overview of repository cluster status from the | You can get an overview of repository cluster status from the | ||||
| {nav Config > Repository Servers} screen. This table shows a high-level | {nav Config > Repository Servers} screen. This table shows a high-level | ||||
| overview of all active repository services. | overview of all active repository services. | ||||
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