Dynamic, Temporary and Consistent Preferred I/O Mode
Original Publication Date: 2005-Feb-23
Included in the Prior Art Database: 2005-Feb-23
Service Prep Mode w/ early I/O selection : the addition to the existing mode is, that the I/O preference could be done xx hours in advance thus freeing the VTS from host I/O w/o preventing the background copy process
Dynamic, Temporary and Consistent Preferred I /O Mode
When a VTS component of the Peer-to-Peer VTS needs to be serviced, the service representative must initiate the Service preparation state. The mode selected determines the impact on host operations.
The VTS is being prepared to be taken off-line. Copies are placed in the Background completed copy queue. These copies are processed "in the background" and must complete before Service Preparation is completed.
Same as Normal, with the exception that copies are placed on the Critical copy queue which will have priority over host jobs. This may result in a performance degradation for Customer jobs, but will expedite the Service Preparation because the copies will be completed faster.
The VTS is being prepared to be taken off-line in the fastest possible manner. Some volumes may be inaccessible because there is not a valid copy available. This selection waits for I/O to finish at the host, but does not wait for the copy process to complete. Customer jobs that attempt to mount volumes that have not yet been copied to the target VTS will fail and need to be restarted when the VTS is available.
This selection will be used to force the state even if copies are being performed and if I/O devices are in a loaded state. There will be volumes that are inaccessible because there is not a valid copy available. Some customer jobs will fail, will have to wait, or will have to be restarted.
The first three modes will result in an unpredictable length of delay as all I/O initiated by the host will be finished and therefore cause undesired idle time for support personnel. The maintenance window, given by Customer, will be unpredictably exceeded and therefore the activities cannot really be estimated in advance. This will lead to customer dissatisfaction and unnecessary costs for the support personnel. Then, last mode is not recommended as it does interrupt host I/O and, thus, terminates the currently running jobs. Beside from the recommendation, Customer will not allow to use that mode.
This invention describes a method to overcome those shortcomings.
This invention suggests the use of an early dynamic, temporary, and transparent preferred I/O mode.
The I/O mode would be set on one VTC (dynamically) . The new mode would only be valid for a certain adjustable timeframe (temporary), so that it would not matter if it was forgotten or entered by mistake. Service prep would be shorter, thus, giving less risk to the customer.
Upon completion of the selection the new state would be distributed to all other VTCs to set them into the same mode (consistent).
A VTS to be serviced could already be prepared using the above method. Once the service window started, the service representative could immediately set the desired VTS into service prep mode using the Immediate mode as there is no host I/O on this VTS.
With this new function, CSR's could be guarantee...