hesela.devHesela / Structured knowledge
Storage Knowledge Corpus
Storage definitions, connected to their evidence.
866 terms · Page 12 of 29
A-Z- JSON
iSCSI Status Sequence Number
An iSCSI Status Sequence Number (StatSN) numbers target responses within one connection for status acknowledgement and recovery.
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JBOD
JBOD (Just a Bunch Of Disks) originally meant disks used without coordinated control software and now usually means an enclosure of drives, with or without RAID functions; for software-managed storage the drives are typically presented individually through a host bus adapter, leaving redundancy to host software.
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JEDEC SSD standards
The JEDEC SSD standards are JESD218 (SSD requirements and endurance test method) and JESD219 (SSD endurance workloads), developed by the JC-64.8 subcommittee, which define the TBW endurance rating and how it is verified for client and enterprise SSD classes.
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Journal checkpoint
In JBD2 terminology, a journal checkpoint writes committed journaled state to its home locations so the corresponding log space can be reclaimed.
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Journal checksum
A journal checksum is an integrity value computed over specified journal records or payloads to detect changes within that coverage.
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Journal revoke record
A journal revoke record identifies a block whose older journaled images must not be replayed over newer uses of that block.
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Kaplan-Meier estimator
The Kaplan-Meier estimator is a nonparametric estimator of the survival function that multiplies conditional survival estimates at observed event times while accounting for right-censored observations.
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Key-value separation
Key-value separation stores values outside the main key index and retains references in that index.
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Key-value SSD
A key-value SSD is a solid-state drive that stores and retrieves variable-length values addressed by a key (up to 16 bytes in the NVMe Key Value command set) through Store, Retrieve, Delete, Exist and List commands, instead of reading and writing fixed-size logical blocks.
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Latent sector error
A latent sector error is an inaccessible sector whose failure remains undiscovered until that location is accessed.
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Lateral charge spreading
Lateral charge spreading is migration of stored charge along a shared trapping layer between neighboring cells in charge-trap NAND.
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Layer-to-layer process variation
Layer-to-layer process variation is fabrication-related variation in cell characteristics between vertical layers of a 3D NAND die.
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LDPC (NAND ECC)
An LDPC code is an error-correcting linear block code defined by a sparse parity-check matrix.
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Least recently used replacement
Least recently used replacement evicts the resident entry whose most recent access is oldest.
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Left-truncation
Left-truncation is selection into a time-to-event sample only after a unit has survived to its observation-entry time.
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Legal hold (storage)
A storage legal hold prevents deletion or replacement of protected data until an authorized action removes the hold, rather than expiring on a preset date.
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Leveled compaction
Leveled compaction organizes sorted data into levels with size targets and merges selected data with overlapping key ranges in a destination level.
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Linearizability
Linearizability requires concurrent operations on an object to behave as a legal sequential execution that preserves the real-time order of non-overlapping operations.
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Linux block-device read-only flag
The Linux block-device read-only flag is a software-controlled device state exposed through block-device ioctls to restrict write access.
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Linux file sealing
Linux file sealing irreversibly restricts selected operations on a supported file, with restrictions shared by all descriptors referring to its inode.
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Linux memfd_create
Linux memfd_create() creates an anonymous volatile file and returns a descriptor for file operations and memory mapping.
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Little's law
Little's law relates time-averaged occupancy L to the operation rate lambda and mean residence time W within the same system boundary.
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LMDB reader table
The LMDB reader table records reader process, thread and transaction identities so page reclamation can respect active snapshots.
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Locally repairable code
A locally repairable code is an erasure code that provides recovery of specified missing fragments from a small subset of surviving fragments.
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Log sequence number
A log sequence number identifies a position in an engine's ordered recovery-log address space.
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Log-likelihood ratio
A log-likelihood ratio is the logarithm of the relative likelihood of two alternatives, used in decoding to express a bit decision and its confidence.
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Log-structured merge-tree
A write-oriented index that buffers updates and merges sorted components over time, trading write batching against read and compaction work.
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Logical decoding
Logical decoding reconstructs database changes from a storage-level log into a representation that a consumer can interpret without the database's physical storage format.
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Logical failover slot
A PostgreSQL logical failover slot is a logical replication slot enabled for synchronization to a physical standby so consumption can resume after promotion.