Abstract: A method for managing lost content change requests (CCRs), the method includes (i) maintaining, by compute entities of a second storage system (SSS), states of executions of multiple CCRs of multiple categories and of multiple SSS reception times; (ii) receiving, from a first storage system (FSS), at a failure indication reception time (FIRT), a failure indication that is indicative of a certain category of the multiple categories. The certain category is associated with a failure of the FSS to receive a response, from the SSS, to a certain CCR of the certain category, that was presumably sent from the FSS to the SSS; (iii) determining, based on states of executions that are related at least to the certain category, when the SSS has completed to execute all CCRs of at least the certain category that were received by the SSS up to the FIRT; and (iv) transmitting, by the SSS, a SSS completion indication that indicates that the SSS has completed to execute all tasks that were received by the SSS up to the FIRT.

Abstract: A method for responding to an access request from a user, the method includes (a) receiving, by a target storage system (TSS) and from a user an access request to access an exposed file system entity (EFSE), the access request is associated with an EFSE external identifier (EEID); (b) applying a logically reversible function on the EEID and on a replication stream identifier (RSID) to provide a TSS internal EFSE identifier (TID); wherein the EFSE was sent to the TSS in association with a replication stream that is identified by the RSID; (c) accessing the EFSE using the TID; and (d) wherein the TID uniquely identifies the EFSE within the TSS.

Abstract: A method for transitioning from asynchronous replication to a synchronous replication, the method includes (i) receiving, by a DSS and following the start of the transitioning, a synchronous update related to a first FSE part; (ii) implementing the synchronous update of the first FSE part; (iii) receiving, by the DSS and following the start of the transitioning, an asynchronous update related to a last version of a second FSE part before the start of the transitioning; (iv) ignoring the asynchronous update when the DSS currently stores a version of the second FSE part that is associated with a timestamp that is indicative of a point in time that exceeds the start of the transitioning; and (v) else—implementing the asynchronous update.

Abstract: A method for updating file system entity (FSE) metadata. The method may include receiving, by a first computing entity, a request to perform a case-sensitive FSE operation that comprises one of (a) adding a case-sensitive version of a name of a FSE to a data structure, or (b) deleting the case-sensitive version of the name of the FSE from the data structure, the data structure comprises multiple name blocks; finding, by the first computing entity, a certain name block of the multiple name blocks that is associated with the case-sensitive version of the name of the FSE.

Abstract: A method for determining size information related one or more file systems stored in a storage system, the method may include (i) sampling one or more logical spaces that are associated with the one or more file systems to provide sampled file system entities (FSEs); wherein a number of samples per sampled FSE is indicative of a size of the sampled FSEs; and (ii) determining logical sizes and physical sizes of different levels of the one or more file systems based on the sampled file system entities.

Abstract: A method for reading a shared clock that is stored in a shared storage space of a storage system, the method may include (a) reading by a compute node a cached value of the shared clock when a time gap before a next update of the shared clock exceeds a time threshold, wherein the cached value is cached in the compute node and is valid during an allowable caching period, wherein the shared clock is shared by a group of compute nodes, wherein a default update of the shared clock has a cycle that exceeds the time threshold; and (b) reading by the compute node a read value of the shared clock when the time gap before the next update of the shared clock does not exceed the time threshold, wherein the read value of the shared clock is stored in the shared storage space.

Abstract: A method for managing access to a shared file system entity (FSE), the method includes (i) managing access requests for reading and writing accessed parts of the FSE, by a current point of access storage system (POASS), the current POASS currently acts as a point of access (POA) for the access requests; wherein stored parts of the FSE are stored at multiple POASSs, the multiple POASSs comprise the current POASS and former POASSs; (ii) determining, by the current POASS and while managing the access requests, to store the stored parts of the FSE at a fewer number of the former POASSs; and (iii) reducing, by two or more of the former POASSs, the number of former POASSs that store the stored parts of the FSE.

Abstract: A method for determining a progress of an execution of a task, the method may include accessing only a portion of a shared task status data structure that (a) is associated with the task, wherein the task is executed by a first plurality of compute elements, and (b) comprises multiple hierarchical levels; wherein an entry of a certain hierarchical level represents an aggregate progress associated with multiple entries of the another hierarchical level; the certain hierarchical level is higher than the other hierarchical level; and determining the progress of the execution of the task based on a content of the portion.

Abstract: A method for contention reduced update of one or more storage system parameters, the method may include (i) concurrently monitoring the one or more storage system parameters (SSPs) by compute entities (CEs); wherein the concurrently monitoring comprises updating, by the CEs, local counters allocated to different SSPs; (ii) updating, by the CEs, sets of shared counter fields with values of the local counters, wherein different sets are allocated to different SSPs; wherein an updating of a set of a shared counter fields by an CE comprises selecting a shared counter field of the set by the CE; and (iii) calculating values of the different SSPs, wherein a calculating of a value of a SSP is based on at least one value of at least one shared counter field of a set that is allocated to the SSP.

Abstract: A method that includes instructing multiple compute entities, by an expansion manager and during a first phase of the stored entity metadata re-balancing, to: lookup any stored entity metadata by using: (a) a current translation function for linking identifiers of stored entities to stored entities metadata; wherein the current translation function is based on a size of a current storage space allocated to stored entities metadata; and (b) a next translation function for linking identifiers of stored entities to stored entities metadata; wherein the next translation function is based on a size of a next storage space allocated to stored entities metadata; wherein the current space is expanded during the expansion of the storage system to provide the next storage space, and to update any stored entity metadata accessed using the current translation function without updating stored entity metadata accessed using the next translation function.

Abstract: A method for recovery point objective compliant star replication, the method includes: obtaining, by a SSS, a user defined RPO value; performing replication iterations to each DSS according to replication schedules of the DSSs, wherein at least two DSSs of the multiple DSSs are assigned with replication schedules having different frequencies of replication iterations; wherein each replication iteration includes sending a content related to a scheduled snapshot; determining a conformance to the RPO, of a time elapsed since a content related to a last common snapshot was replicated to each one of the multiple DSSs; and performing a non-scheduled common (NSC) replication iteration to each of the multiple DSSs to prevent a violation of the RPO, wherein the NSC replication iteration includes sending content related to a NSC snapshot to each one of the multiple DSSs.

Abstract: A method for monitoring largest file system entities of a file system that is stored in a storage system, the method may include populating, during multiple population iterations, a cache of the storage system with largest file system entities metadata; wherein a current population iteration of the multiple population iterations may include pushing, to a heap, metadata related to a set of one or more file system entities that are children of a parent file system entity that was deemed a largest file system entity of a last population iteration that preceded the current population iteration; popping the heap to provide a current largest file system entity; and storing metadata related to the current largest file system entity in the cache.

Abstract: A method for retrieving a file system entity at a presence of snapshot restore in a history of the file system entity , the method may include (i) receiving a request to obtain a content of the file system entity (FSE) at a certain point in time (PIT); and (ii) retrieving the content of the FSE at the certain point in time, wherein the retrieving comprises searching for FSE content segments to be included in a response to the request, wherein each FSE content segment has a write time that does not exceed the certain PIT, each FSE content segment is not included in a relevant blind period of time that is associated with a reversible snapshot restore operation, and fulfills another timing criterion.

Abstract: A method for contention reduced update of one or more storage system parameters, the method may include (i) concurrently monitoring the one or more storage system parameters (SSPs) by compute entities (CEs); wherein the concurrently monitoring comprises updating, by the CEs, local counters allocated to different SSPs; (ii) updating, by the CEs, sets of shared counter fields with values of the local counters, wherein different sets are allocated to different SSPs; wherein an updating of a set of a shared counter fields by an CE comprises selecting a shared counter field of the set by the CE; and (iii) calculating values of the different SSPs, wherein a calculating of a value of a SSP is based on at least one value of at least one shared counter field of a set that is allocated to the SSP.

Abstract: A method for determining size information related one or more snapshots related to file systems stored in a storage system, the method may include (a) sampling one or more combinations of points in time and logical spaces, the logical spaces are associated with the one or more file systems to provide sampled combinations of sampled portions of file system entities (FSEs) and sampled points in time; (b) searching for relevant snapshots that are relevant to the sampled combinations to provide relevant snapshots at the sampled points in time; and (c) determining physical sizes of the relevant snapshots at the sampled point in time; wherein a number of samples per sampled FSE is indicative of a size of the sampled FSEs.

Abstract: A method for lock metadata re-balancing upon an expansion of a storage system, the method may include instructing multiple compute entities, by an expansion manager and during a first phase of the lock metadata re-balancing, to acquire locks by using: (a) a current translation function for linking addresses of current lock metadata units (LMUs) to identifiers of stored entities; wherein the current translation function is based on a size of a current storage space allocated to the lock metadata; and (b) a next translation function for linking addresses of new LMUs to identifiers of stored entities; wherein the new translation function is based on a size of a new storage space allocated to the lock metadata; wherein the current space is expanded during the expansion of the storage system to provide the next storage space.

Abstract: A method for determining size information related one or more file systems stored in a storage system, the method may include (i) sampling one or more logical spaces that are associated with the one or more file systems to provide sampled file system entities (FSEs); wherein a number of samples per sampled FSE is indicative of a size of the sampled FSEs; and (ii) determining logical sizes and physical sizes of different levels of the one or more file systems based on the sampled file system entities.

Abstract: A method for determining size information related one or more snapshots related to file systems stored in a storage system, the method may include (a) sampling one or more combinations of points in time and logical spaces, the logical spaces are associated with the one or more file systems to provide sampled combinations of sampled portions of file system entities (FSEs) and sampled points in time; (b) searching for relevant snapshots that are relevant to the sampled combinations to provide relevant snapshots at the sampled points in time; and (c) determining physical sizes of the relevant snapshots at the sampled point in time; wherein a number of samples per sampled FSE is indicative of a size of the sampled FSEs

Abstract: A method for maintaining an availability of a storage system, the method may include obtaining, by a control module of the storage system, problem related information generated by one or more compute nodes of the storage system, the problem related information is indicative of one or more problems associated with an execution of one or more storage operations; determining, by the control module and based on the problem related information, whether to forbid an execution of a storage operation of the one of more storage operations; and updating, by the control module, and based on the determining, a forbidden storage operation data structure that is accessible to the compute nodes of the storage system.

Abstract: A method for hierarchical workload allocation in a storage system, the method may include determining to reallocate a compute workload of a current compute core of the storage system; wherein the current compute core is responsible for executing a workload allocation unit that comprises one or more first type shards; and reallocating the compute workload by (a) maintaining the responsibility of the current compute core for executing the workload allocation unit, and (b) reallocating at least one first type shard of the one or more first type shards to a new workload allocation unit that is allocated to a new compute core of new compute cores.