Abstract: Modifying a clone image of a dataset, including: generating, based on metadata describing one or more updates to a dataset, a tracking copy of replica data on a target data repository; generating, after receiving an indication to begin accepting modifications to the tracking copy of the replica data, a cloned image of the dataset that is modifiable without modifying the tracking copy of the replica data; and responsive to a storage operation directed to the target data repository, modifying the cloned image of the dataset without modifying the tracking copy of the replica data.

Abstract: Managing storage systems that are synchronously replicating a dataset, including: detecting a change in membership to the set of storage systems synchronously replicating the dataset; and applying one or more membership protocols to determine a new set of storage systems to synchronously replicate the dataset, wherein the one or more membership protocols include a quorum protocol, an external management protocol, or a racing protocol, and wherein one or more I/O operations directed to the dataset are applied to a new set of storage systems.

Abstract: Transitioning between replication sources for data replication operations, including: delaying a transition from using a first data repository as a source for data replication to using a second data repository as the source for data replication after detecting that one or more storage operations directed to the first data repository have not been replicated to the second data repository; and promoting the second data repository as the source for data replication such that storage operations received after completing the transition are directed to the second data repository.

Abstract: Cloning a tracking copy of replica data, including receiving, at a target data repository from a source data repository, metadata describing one or more updates to a dataset stored within the source data repository; generating, based on the metadata describing the one or more updates to the dataset, a tracking copy of replica data on the target data repository; and generating, based on the tracking copy, a cloned image of the dataset that is modifiable without modifying the tracking copy of the replica data.

Abstract: Determining active membership among a set of storage systems synchronously replicating a dataset, where determining active membership includes: determining that a membership event corresponds to a change in membership to the set of storage systems synchronously replicating the dataset; applying, in dependence upon the membership event, one or more membership protocols to determine a new set of storage systems to synchronously replicate the dataset; and for one or more I/O operations directed to the dataset, applying the one or more I/O operations to the dataset synchronously replicated by the new set of storage systems.

Abstract: Resilient mediation between storage systems replicating a dataset, including: receiving, by a mediation service from one or more storage systems that synchronously replicate a dataset, a request to resolve which storage system continues to service a dataset after the request; and sending, from the mediation service to at least one of the storage systems, a positive mediation result, wherein: the storage systems that received the positive mediation result continue to process data storage requests directed to the dataset, and the storage systems that did not receive a positive mediation result from the mediation service do not continue to process data storage requests directed to the dataset.

Abstract: A method of data loss prevention during transitions from a replication source, the method including: initiating a transition from using a first data repository as a source for data replication to using a second data repository as the source for data replication; prior to completing the transition and responsive to determining that one or more storage operations directed to the first data repository have not been replicated to the second data repository, delaying transition of the second data repository as the source for data replication; and responsive to completing the transition, promoting the second data repository as the source for data replication such that all storage operations received after completing the transition are directed to the second data repository.

Abstract: Mediating between storage systems synchronously replicating a dataset, including: requesting, by a first storage system in response to detecting a triggering event, a lock for a shared resource from a mediation service; requesting, by a second storage system in response to detecting the triggering event, the lock for the shared resource from the mediation service; and responsive to acquiring the lock from the mediation service, the first storage system, instead of the second storage system, processing data storage requests directed to the dataset that is synchronously replicated across the first storage system and the second storage system.

Abstract: A storage system switching mediators within a storage system synchronously replicating data, where the switching between mediators includes: determining, among one or more of the plurality of storage systems, a change in availability of a first mediator service, wherein one or more of the plurality of storage systems are configured to request mediation from the first mediator service; communicating, among the plurality of storage systems and responsive to determining the change in availability of the first mediator service, a second mediator service to use in response to a fault; and switching, in dependence upon the change in availability of the first mediator service, from the first mediator service to the second mediator service.

Abstract: Establishing a synchronous replication relationship between two or more storage systems, including: identifying, for a dataset, a plurality of storage systems across which the dataset will be synchronously replicated; configuring one or more data communications links between each of the plurality of storage systems to be used for synchronously replicating the dataset; exchanging, between the plurality of storage systems, timing information for at least one of the plurality of storage systems; and establishing, in dependence upon the timing information for at least one of the plurality of storage systems, a synchronous replication lease, the synchronous replication lease identifying a period of time during which the synchronous replication relationship is valid.

Abstract: A method of managing host mappings for replication endpoints, the method including: identifying a target storage system replicating a source dataset of a source storage system, wherein a first host is mapped to the source dataset on the source storage system; providing, to the target storage system and in dependence upon a mapping of the first host to the source dataset, configuration information for connecting to a second host; and implementing, in response to a triggering event, a mapping of the second host to a replica dataset on the target storage system.

Abstract: A method of mapping equivalent hosts at distinct replication endpoints, the method including: receiving an indication that a first host mapped to a source dataset at a replication source is equivalent to a second host for a replica dataset at a replication target of the source dataset; transmitting, from the replication source to the replication target and based on an update to the source dataset received from the first host, metadata describing the update to the source dataset; and mapping, based on the indication that the first host mapped to the source dataset at the replication source is equivalent to the second host for the replica dataset at the replication target, the second host to the replica dataset at the replication target of the source dataset.

Abstract: A storage system switching mediators within a storage system synchronously replicating data, where the switching between mediators includes: determining, among one or more of the plurality of storage systems, a change in availability of a first mediator service, wherein one or more of the plurality of storage systems are configured to request mediation from the first mediator service; communicating, among the plurality of storage systems and responsive to determining the change in availability of the first mediator service, a second mediator service to use in response to a fault; and switching, in dependence upon the change in availability of the first mediator service, from the first mediator service to the second mediator service.

Abstract: Verifying that data has been correctly replicated to a replication target, including: replicating a dataset stored at a first computing system to a second computing system; and determining, based at least on a comparison of a first hash and a second hash, validity of the dataset stored at the second computing system, wherein the first hash is generated by applying a hash function to a copy of the dataset that is stored at the first computing system and the second hash is generated by applying the hash function to a copy of the dataset that is stored at the second computing system.

Abstract: A storage system switching between mediation models within a storage system, where the switching between mediation models includes: determining, among one or more of the plurality of storage systems, a change in availability of a mediator service, wherein one or more of the plurality of storage systems are configured to request mediation from the mediator service in response to a fault; and communicating, among the plurality of storage systems and responsive to determining the change in availability of the mediator service, a fault response model to be used as an alternate to the mediator service among one or more of the plurality of storage systems.

Abstract: Performing replicated data integrity, including: generating, at a first computer system, a local hash of a local dataset; replicating the local dataset; receiving, at the first computer system from a second computer system, a remote hash of a remote dataset generated from the local dataset replicated from the first computer system; and determining, based at least on a comparison of the local hash of the local dataset with the remote hash of the remote dataset, validity of the remote dataset generated from the local dataset replicated from the first computer system.

Abstract: A storage system switching between mediation models within a storage system, where the switching between mediation models includes: determining, among one or more of the plurality of storage systems, a change in availability of a mediator service, wherein one or more of the plurality of storage systems are configured to request mediation from the mediator service in response to a fault; and communicating, among the plurality of storage systems and responsive to determining the change in availability of the mediator service, a fault response model to be used as an alternate to the mediator service among one or more of the plurality of storage systems.

Abstract: Establishing a synchronous replication relationship between two or more storage systems, including: identifying, for a dataset, a plurality of storage systems across which the dataset will be synchronously replicated; configuring one or more data communications links between each of the plurality of storage systems to be used for synchronously replicating the dataset; exchanging, between the plurality of storage systems, timing information for at least one of the plurality of storage systems; and establishing, in dependence upon the timing information for at least one of the plurality of storage systems, a synchronous replication lease, the synchronous replication lease identifying a period of time during which the synchronous replication relationship is valid.

Abstract: Continuous data protection, including sending, to a target data repository from a source data repository, metadata describing one or more updates to one or more datasets stored within the source data repository; generating, based on the metadata describing the one or more updates to the one or more datasets, an ordered log of metadata describing an ordered application of the one or more updates to the one or more datasets; and generating, on the source data repository and based on the ordered log of metadata, the one or more datasets in accordance with the one or more updates corresponding to a specified point in time.

Abstract: This invention concerns a neurosurgical kit comprising a catheter (1) and a guide tube (2). The catheter (1) comprises a distal section of tubing (11) having a distal end with a port or ports for delivering fluid to a target site within the brain. The distal section of tubing (11) has an outer diameter that is smaller than an internal diameter of the guide tube (2). The catheter (1) and guide tube (2) are arranged such that, when the catheter (1) is inserted into the guide tube (2) to locate the port or ports at the target site, a recess (14) is provided in a distal end section of the guide tube (2) between the guide tube (2) and the distal section of tubing (11) of the catheter (1).