STORAGE DEVICE SWAP IN A MULTIPLE COMPUTING CLUSTER ENVIRONMENT USING CROSS SYSTEM COMMUNICATION

Storage device swap in a multiple computing cluster environment using cross system communication includes sending, by a first host device of a first computing cluster of a plurality of computing clusters, a swap trigger command to one or more storage devices shared across the plurality of computing clusters indicating that a swap event is to be triggered. The swap trigger command identifies the one or more storage devices to participate in the swap event. The first host device receives a signal to trigger the swap event from a storage controller associated with the one or more storage devices, a signal to trigger the swap event.

BACKGROUND

The present disclosure relates to methods, apparatus, and products for storage device swap in a multiple computing cluster environment using cross system communication.

SUMMARY

According to embodiments of the present disclosure, various methods, apparatus and products for storage device swap in a multiple computing cluster environment using cross system communication are described herein. In some aspects, storage device swap in a multiple computing cluster environment using cross system communication includes sending, by a first host device of a first computing cluster of a plurality of computing clusters, a swap trigger command to one or more storage devices shared across the plurality of computing clusters indicating that a swap event is to be triggered. The swap trigger command identifies the one or more storage devices to participate in the swap event. The first host device receives a signal to trigger the swap event from a storage controller associated with the one or more storage devices, a signal to trigger the swap event.

DETAILED DESCRIPTION

A computing system is often in communication over a network with one or more storage systems for storing and accessing data used during operation of the computing system. The different storage systems are often located in different geographical locations. Each storage system typically includes one or more storage devices (e.g., disk drives) controlled by a storage controller. Storage replication allows for maintaining redundant copies of data on two different storage systems to allow for continuous availability in the event of a failure of one of the storage systems. Switching from usage of one storage system to another storage system is often referred to as a swap event. The switching from one storage system to another storage system in the event of a failure of the storage system is often referred to as an unplanned swap event. An example of an operating system including such swap capability is the HyperSwap function provided by the z/OS operating system offered by International Business Machines™. A sysplex refers to a computing cluster of independent instances of an operating system. The HyperSwap function provides for continuous availability in the event of disk failures by maintaining synchronous copies of all primary disk volumes on one or more secondary storage controllers. During data replication, data is copied from a source volume to one or more target volumes. The source volume and target volumes that contain copies of the same data are collectively referred to as a copy set. Disk failures can be hidden from applications by the HyperSwap function automatically swapping form one set of disk volumes to another as a result of triggering a swap event.

Peer-to-peer remote copy (PPRC) is a protocol used to replicate a primary storage volume to a secondary storage volume. The primary storage volume and secondary storage volume are often connected together through a communication link called a PPRC path. To facilitate configuration of storage devices, a storage device partitions its possible logical volumes into groups of volumes. Each group of volumes is referred to as a logical subsystem (LSS). An LSS is uniquely identified within the storage system by an LSS identifier that typically is a numerical value. To establish remote mirror and copy pairs, a logical path is established between the associated LSS pair.

In a swap environment (e.g., a HyperSwap environment) with storage devices shared across multiple computing clusters (e.g., sysplexes), a need exists for each computing cluster to be aware when another computing cluster has swapped. This need especially exists for a system which allow each computing cluster to utilize independent swap sessions, and/or each swap session is on a sysplex basis which communicate with each other only through the shared storage devices. In existing procedures when one session/sysplex swaps, the other session/sysplex is triggered to swap by the first session soft fencing the shared devices, receives a soft fence unit check, and automatically swaps. Soft fencing prevents unintended access to the storage device by preventing most I/O operations (e.g., reading and writing data) to the storage device.

However, if there is no or little I/O activity on the shared storage device, the swap may not occur immediately. For example, if I/O activity to some other non-HyperSwap protect device is hanging, an application that normally performs I/O operations to shared devices may be delayed. A disadvantage of delayed swapping may include, for example, an undesirable user experience caused by confusion regarding the delayed swap. Another example of a disadvantage that may occur due to a delayed swap is that it can expose existing or new timing windows, e.g., if a second sysplex is down before swapping, a mix of PPRC primary and secondary devices within their configuration may require manual intervention to repair. Another potential disadvantage of delayed swapping is that a user may be unable to initiate cleanup activities such as restarting mirroring from a second storage site to a first storage site until all sysplexes have swapped to the second storage site.

One or more embodiments provide for a method of automatically swapping of storage devices in a multiple computing cluster environment based on a command, such as a channel command word (CCW), from host devices on one computing cluster (e.g., a sysplex) to communicate to the computing clusters sharing the same storage devices that a swap is occurring. In a particular embodiment, when any computing cluster performs a planned or unplanned swap event, the computing cluster sends a new command called a Set Swap Trigger to the source storage devices and the target storage devices to indicate that a swap is occurring. In a particular embodiment, a storage controller associated with the storage devices reacts to the Set Swap Trigger command and raises a summary unit check event to all attached host devices. A summary unit check events triggers the storage devices returning their current states. Each host device detects the summary unit check event for the Set Swap Trigger, and triggers unplanned an HyperSwap operation if the event affects a HyperSwap primary storage device and a swap is not already active. In a particular embodiment, as an alternative to the summary unit check, an attention interrupt is sent by the storage controller and the host devices read the attention interrupt, for example using a Read Subsystem Data for Message Buffer.

In an embodiment, each sysplex issues a command to one or more storage devices involved in a swap with an indication that a swap event should be triggered. A storage controller for the one or more storage devices reacts to the command and raises signals to all attached hosts to trigger an unplanned swap operation. In a particular embodiment, the command is used on a LSS basis. In a particular embodiment, the storage devices in the LSS undergoing the swap are identified using a device bitmap supplied with the command.

Processor set 110 includes one, or more, computer processors of any type now known or to be developed in the future. Such computer processors as well as graphic processors, accelerators, coprocessors, and the like are sometimes referred to herein as a processing device. A processing device and a memory operatively coupled to the processing device are sometimes referred to herein as an apparatus. Processing circuitry 120 may be distributed over multiple packages, for example, multiple, coordinated integrated circuit chips. Processing circuitry 120 may implement multiple processor threads and/or multiple processor cores. Cache 121 is memory that is located in the processor chip package(s) and is typically used for data or code that should be available for rapid access by the threads or cores running on processor set 110. Cache memories are typically organized into multiple levels depending upon relative proximity to the processing circuitry. Alternatively, some, or all, of the cache for the processor set may be located “off chip.” In some computing environments, processor set 110 may be designed for working with qubits and performing quantum computing.

Referring now to FIG. 2, FIG. 2 sets forth another example computing environment according to aspects of the present disclosure. Computing environment 200 includes a first computing cluster (Sysplex 1) 202A having a first host device 203A and a second computing cluster (Sysplex 2) 202B having a second host device 203B. In a particular embodiment, the first host device 203A and the second host device 203B includes the computer 101 described with respect to FIG. 1. The first host device 203A includes a first swap management module 204A and the second host device 203B include a second swap management module 204B. In a particular embodiment, the first swap management module 204A and the second swap management module 204B includes the swap management module 107 described with respect to FIG. 1.

The first computing cluster 202A and the second computing cluster 202B are each in communication with a set of source storage devices (or volumes)(H1) 206. In a particular embodiment, each of first computing cluster 202A and the second computing cluster 202B are in communication with the shared source storage device 212B via FICON connections. The set of source storage devices 206 are in communication with a set of target storage devices (or volumes) (H2) 208. In a particular embodiment, the set of source storage devices 206 are in communication with the set of target storage devices 208 via PPRC connections. In a particular embodiment, the set of source storage devices 206 and the set of target storage devices 208 are located at a different location or site. In one or more embodiments, each of the set of source storage devices 206 and the set of target storage devices 208 include one or more associated storage controllers (not shown). In one or more embodiments, the second computing cluster 202B is a foreign computing cluster in relation to the first computing cluster 202A.

The set of source storage devices 206 includes source storage devices 212A-212C in which source storage device 212A is a dedicated source storage device for the first computing cluster 202A, the source storage device 212C is a dedicated source storage device for the second computing cluster 202B, and the shared source storage device 212B is a shared source storage device by both the first computing cluster 202A and the second computing cluster 202B. The set of target storage devices 208 includes target storage devices 214A-214C in which target storage device 214A is a dedicated target storage device for the first computing cluster 202A, the target storage device 214C is a dedicated target storage device for the second computing cluster 202B, and the target storage device 214B is a shared target storage device by both the first computing cluster 202A and the second computing cluster 202B. The set of source storage devices 206 include a first storage controller 216A in communication with the first host device 203A and the second host device 203B for controlling the source storage devices 212A-212C. The set of target storage devices 208 include a second storage controller 216B in communication with the first host device 203A and the second host device 203B for controlling the target storage devices 214A-214C. Although various embodiments are illustrated using two computing clusters for simplicity of explanation, in other embodiments more than two computing clusters are used.

In an example operation, a need exists to perform a swap from the shared source storage device 212B of the shared source storage device 212B to the shared target storage device 214B of the set of target storage devices 208. In a particular embodiment, the shared source storage device 212B and the shared target storage device 214B are grouped as an LSS. The first host device 203A sends a swap trigger command to the shared source storage device 212B and the shared target storage device 214B indicating that a swap event is to be triggered. The swap trigger command includes information identifying the shared source storage device 212B and the shared target storage device 214B that are to participate in the swap event. In a particular embodiment, the information identifying the shared source storage device 212B and the shared target storage device 214B is a bitmap.

The first storage controller 216A reacts to receiving the swap trigger command by raising signals to the first host device 203A and the second host device 203B to trigger an unplanned swap event. In a particular embodiment, the signal to trigger the swap event is a summary unit check event. In another particular embodiment, the signal to trigger the swap event is an attention interrupt. The first host device 203A receives the signal to trigger the swap event from the first storage controller 216A, and triggers the swap event responsive to receive the signal.

Referring now to FIG. 3, FIG. 3 sets forth a flowchart of an example process for host device swap processing according to aspects of the present disclosure. When a planned or unplanned HyperSwap occurs 300, for each LSS in the HyperSwap configuration, a host device builds 302 a bitmap of storage devices in the HyperSwap configuration for the particular LSS. The bitmap identifies which of the storage devices in the current LSS are in the current HyperSwap configuration. The host device issues 304 a set swap trigger command the primary LSS and the secondary LSS using the built bitmap. The processing ends 306 for each LSS in the HyperSwap configuration.

The host device performs 308 the HyperSwap steps to complete the HyperSwap operation. In particular embodiments, the HyperSwap sets include quiescing of I/O operations, failover, swapping of unit control blocks (UCBs) in the HyperSwap identification array from primary to secondary, resuming of I/O operations, and cleanup operations. The process then ends 310.

Referring now to FIG. 4, FIG. 4 sets forth a flowchart of an example process for host device summary unit check processing according to aspects of the present disclosure. The host device receives 400 a summary unit check message from a storage controller. The host device determines 404 whether to set a swap trigger event based on the summary unit check message. If no swap trigger event is to be set, the example process ends 412. If a swap trigger event is to be set, the host device calls 408 an IOS HyperSwap initiation service for each storage device in the affected LSS as further described with respect to FIG. 5 and the example process ends 410 for the current storage device in the affected LSS. Once all storage devices in the affected LSS have been evaluated, the example process ends 412.

Referring now to FIG. 5, FIG. 5 sets forth a flowchart of an example process for host device swap service initiation according to aspects of the present disclosure. During an IOS HyperSwap Initiation Service call 500, a host device determines 502 whether a HyperSwap operation is already in progress. If a HyperSwap operation is already in progress, the example process ends 512. If a HyperSwap operation is not already in progress, the host device determines 504 whether hardware reserve support is enabled. Enablement of hardware reservice support ensures that active hardware reserves on primary PPRC devices are properly transferred to a new primary device after a HyperSwap operation. If hardware reserve support is not enabled, the example process ends 512.

If hardware reserve support is enabled, the host device determines 506 if HyperSwap is enabled. If Hyperswap is not enabled, the example process ends 512. If HyperSwap is enabled, the host device determines 508 if the storage device is monitored by HyperSwap. If the storage device is not monitored by HyperSwap, the example process ends 512. If the storage device is monitored by HyperSwap, the host device raises 510 an event notification for HyperSwap trigger to initiate a HyperSwap operation and the example process ends 512.

Referring now to FIG. 6, FIG. 6 sets forth an example set swap trigger command 600 according to aspects of the present disclosure. The example set swap trigger command 600 includes a command field 602, a flags field 604, an action field 606, a first reserved field 608, a second reserved field 610, an LSS field 612, a third reserved field 614, and a device bitmap 616. The command field 602 identifies the set swap trigger command 600, and the action field 606 identifies an action (e.g., a swap) to be taken in response to receiving the set swap trigger command 600. The LSS field 612 identifies the LSS to be involved in the swap operation. The device bitmap 616 includes bit values indicating the storage devices to be involved in the swap operation. In a particular embodiment, the set swap trigger command 600 is issued to any device in an LSS, and the device bitmap 616 indicates the storage devices in the LSS that are affected by the HyperSwap event.

Referring now to FIG. 7, FIG. 7 sets forth a flowchart of an example process for storage device swap in a multiple computing cluster environment using cross system communication according to aspects of the present disclosure. In the example process of FIG. 7, a first host device of a first computing cluster of a plurality of computing clusters sends 702 a swap trigger command to one or more storage devices shared across the plurality of computing clusters indicating that a swap event is to be triggered. The swap trigger command identifies the one or more storage devices to participate in the swap event. In a particular embodiment, the swap trigger command includes a bitmap identifying the one or more storage devices to participate in the swap event.

In a particular embodiment, the one or more storage devices comprise a logical subsystem (LSS). In another particular embodiment, the one or more storage devices comprise a source storage device and a target storage device.

The first host device receives 704 a signal to trigger the swap event from a storage controller associated with the one or more storage devices. In a particular embodiment, the storage controller is configured to send the signal to trigger the swap event responsive to receiving the swap trigger command. In a particular embodiment, the signal to trigger the swap event is a summary unit check event. In another particular embodiment, the signal to trigger the swap event is an attention interrupt.

Referring now to FIG. 8, FIG. 8 sets forth a flowchart of another example process for storage device swap in a multiple computing cluster environment using cross system communication according to aspects of the present disclosure. The process of FIG. 8 is similar to the process described with respect to FIG. 7 and further includes triggering 802 the swap event responsive to receiving the signal to trigger the swap event. In a particular embodiment, the swap event comprises an unplanned swap event.