diff --git a/api-guide/source/server_concepts.rst b/api-guide/source/server_concepts.rst index e426fc9d56..0be7d63acc 100644 --- a/api-guide/source/server_concepts.rst +++ b/api-guide/source/server_concepts.rst @@ -399,63 +399,6 @@ compute host to another including shelve, resize, migrations and evacuate. The following use cases demonstrate the intention of the actions and the consequence for operational procedures. -User doesn't want to be charged when not using a server -------------------------------------------------------- - -Sometimes a user does not require a server to be active for a while, -perhaps over a weekend or at certain times of day. -Ideally they don't want to be billed for those resources. -Just powering down a server does not free up any resources, -but shelving a server does free up resources to be used by other users. -This makes it feasible for a cloud operator to offer a discount when -an server is shelved. - -When the user shelves a server the operator can choose to remove it -from the compute hosts, i.e. the operator can offload the shelved server. -When the user's server is unshelved, it is scheduled to a new -host according to the operators policies for distributing work loads -across the compute hosts, including taking disabled hosts into account. -This will contribute to increased overall capacity, freeing hosts that -are ear-marked for maintenance and providing contiguous blocks -of resources on single hosts due to moving out old servers. - -Shelving a server is not normally a choice that is available to -the cloud operator because it affects the availability of the server -being provided to the user. - -User resizes server to get more resources ------------------------------------------ - -Sometimes a user may want to change the flavor of a server, e.g. change -the quantity of cpus, disk, memory or any other resource. This is done -by rebuilding the server with a new flavor. As the server is being -moved, it is normal to reschedule the server to another host -(although resize to the same host is an option for the operator). - -Resize involves shutting down the server, finding a host that has -the correct resources for the new flavor size, moving the current -server (including all storage) to the new host. Once the server -has been given the appropriate resources to match the new flavor, -the server is started again. - -After the resize operation, when the user is happy their server is -working correctly after the resize, the user calls Confirm Resize. -This deletes the backup server that was kept on the source host. -Alternatively, the user can call Revert Resize to delete the new -resized server, and restore the back up that was stored on the source -host. If the user does not manually confirm the resize within a -configured time period, the resize is automatically confirmed, to -free up the space the backup is using on the source host. - -As with shelving, resize provides the cloud operator with an -opportunity to redistribute work loads across the cloud according -to the operators scheduling policy, providing the same benefits as -above. - -Resizing a server is not normally a choice that is available to -the cloud operator because it changes the nature of the server -being provided to the user. - Cloud operator needs to move a server ------------------------------------- @@ -564,3 +507,60 @@ Evacuating a server is solely in the domain of the cloud operator because it must be performed in coordination with other operational procedures to be safe. A user is not normally aware of compute hosts but is adversely affected by their failure. + +User resizes server to get more resources +----------------------------------------- + +Sometimes a user may want to change the flavor of a server, e.g. change +the quantity of cpus, disk, memory or any other resource. This is done +by rebuilding the server with a new flavor. As the server is being +moved, it is normal to reschedule the server to another host +(although resize to the same host is an option for the operator). + +Resize involves shutting down the server, finding a host that has +the correct resources for the new flavor size, moving the current +server (including all storage) to the new host. Once the server +has been given the appropriate resources to match the new flavor, +the server is started again. + +After the resize operation, when the user is happy their server is +working correctly after the resize, the user calls Confirm Resize. +This deletes the backup server that was kept on the source host. +Alternatively, the user can call Revert Resize to delete the new +resized server, and restore the back up that was stored on the source +host. If the user does not manually confirm the resize within a +configured time period, the resize is automatically confirmed, to +free up the space the backup is using on the source host. + +As with shelving, resize provides the cloud operator with an +opportunity to redistribute work loads across the cloud according +to the operators scheduling policy, providing the same benefits as +above. + +Resizing a server is not normally a choice that is available to +the cloud operator because it changes the nature of the server +being provided to the user. + +User doesn't want to be charged when not using a server +------------------------------------------------------- + +Sometimes a user does not require a server to be active for a while, +perhaps over a weekend or at certain times of day. +Ideally they don't want to be billed for those resources. +Just powering down a server does not free up any resources, +but shelving a server does free up resources to be used by other users. +This makes it feasible for a cloud operator to offer a discount when +an server is shelved. + +When the user shelves a server the operator can choose to remove it +from the compute hosts, i.e. the operator can offload the shelved server. +When the user's server is unshelved, it is scheduled to a new +host according to the operators policies for distributing work loads +across the compute hosts, including taking disabled hosts into account. +This will contribute to increased overall capacity, freeing hosts that +are ear-marked for maintenance and providing contiguous blocks +of resources on single hosts due to moving out old servers. + +Shelving a server is not normally a choice that is available to +the cloud operator because it affects the availability of the server +being provided to the user.