Systems and methods are described for enabling garbage collection on data storage systems. Traditional garbage collection often attempts to track use of data items on an individual level, deleting each item when it is no longer used. In distributed systems, tracking use on an individual level is difficult, and may require centralized knowledge across the system with respect to individual data items. Provided herein is a “coarse-grained” garbage collection mechanism, which divides objects into logical groups referred to as “roots.” Each root has a life cycle. While active, new data can be stored in a root. While inactive, use of data within a root can cause that date to be copied to a different, active root. When the system detects that data hasn't been used in an inactive root for a threshold period, the root can be considered “dead” and data within the root may be deleted.

Various implementations described herein relate to systems and methods for managing metadata for conditional update, including adding conditional entry to a list in an in-memory journal for a conditional update associated with a garbage collection write, configuring a base entry in the list to point to the conditional entry, and in response to determining that the conditional update is resolved such that a physical location identified in the conditional entry is valid, freeing the conditional entry.

An illustrative method includes an object retention management system establishing a retention policy for a bucket of an object-based storage system, detecting an operation that causes an object to be stored within the bucket, and applying, based on the detecting of the operation, the retention policy to the object, the retention policy preventing the object from being deleted or overwritten for a predefined time duration.

Techniques are provided for serializing replication operations. A plurality of operations are implemented upon a first storage object and are replicated as a plurality of replication operations. An order with which the plurality of replication operation are to be executed upon a second storage object is determined. Execution of the plurality of replication operations upon the second storage object is serialized according to the order.

A technique manages data within a storage array. The technique involves forming a hybrid tier within the storage array, the hybrid tier including SSD storage and HDD storage. The technique further involves, after the hybrid tier is formed, providing hybrid ubers (or Redundant Array of Independent Disks (RAID) extents) from the SSD storage and the HDD storage of the hybrid tier. The technique further involves, after the hybrid ubers are provided, accessing the hybrid ubers to perform data storage operations.

A nonvolatile semiconductor memory device comprises a cell unit including a first and a second selection gate transistor and a memory string provided between the first and second selection gate transistors and composed of a plurality of serially connected electrically erasable programmable memory cells operative to store effective data; and a data write circuit operative to write data into the memory cell, wherein the number of program stages for at least one of memory cells on both ends of the memory string is lower than the number of program stages for other memory cells, and the data write circuit executes the first stage program to the memory cell having the number of program stages lower than the number of program stages for the other memory cells after the first stage program to the other memory cells.

A plurality of zone reset counters and a global reset counter are maintained. A zone reset counter represents a number of times a respective zone of a memory device has been reset. The global reset counter represents a measure of central tendency of the plurality of zone reset counters. A write command directed to a target zone of the memory device is received, and responsive to determining that a target portion of the target zone is not open, a value of the zone reset counter of het target zone is compared to the value of the global reset counter. If the value of the target zone reset counter equals or exceeds the value of the global reset counter, a portion from a free block list is allocated to the target zone. The allocated portion has a highest program erase count among the one or more portions in free block list.

The present invention provides a control method of a flash memory controller, wherein the flash memory controller is configured to access a flash memory module, and the control method includes the steps of: receiving a settling command from a host device to configure a portion space of the flash memory module as a zoned namespace; receiving a write command from the host device to write data corresponding a first zone into a plurality of blocks of the flash memory module, wherein an access mode chose by the flash memory controller is determined based on a size of each zone and a size of each block.

Systems and methods for replacing and testing a data storage device are disclosed. In disclosed embodiments, a system including a data storage array (DSA) including a plurality of data storage devices (DSDs) in an enclosure. The system further includes an I/O server coupling the DSA to a client node and configured to provide data access between the client node and the DSA. The system further includes a management server coupled to the DSA, configured to detect a failed DSD in the DSA, detect a replacement DSD in the enclosure that replaces the failed DSD, and add the replacement DSD to a logical path of the DSA. The management server is further configured to display an indication of a state of the DSA based on the comparing.

A method of operating a data storage device includes programming non-fully programmed memory blocks at a point in time when a reference time elapses from a point in time when each of the memory blocks is physically erased, acquiring a first interval and a second interval, calculating a disturb index based on the first interval and the second interval, selecting a victim block for garbage collection based on the disturb index, and copying valid page data of the victim block into a free block. The first interval is defined by a point in time when each of the memory blocks is physically erased and a point in time when each of the memory blocks is fully programmed. The second interval is an interval during which a fully programmed state is maintained after a point in time when each of the memory blocks is fully programmed.