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Storage Knowledge Corpus
Storage definitions, connected to their evidence.
866 terms · Page 10 of 29
A-Z- JSON
HDF5 virtual dataset
An HDF5 virtual dataset maps selections from source datasets into a single logical array without storing those source values in the virtual mapping itself.
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Head-disk interface (HDI)
The head-disk interface is the interacting region between an HDD's head-carrying slider and rotating disk surface.
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Heat-assisted magnetic recording (HAMR)
Heat-assisted magnetic recording uses localized optical heating to enable magnetic writing of high-anisotropy HDD media.
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Hedged request
A hedged request is a redundant copy dispatched after an initial request remains unfinished for a chosen delay, allowing an eligible response to complete the operation.
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Helical scan recording
Helical scan recording writes short, slanted tracks across a tape that moves slowly past a rotating head drum (scanner), so the heads move far faster relative to the tape than the tape moves; it is used in DAT-family data cartridges and in some video formats.
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Helium leak port
Helium leak port is an unverified legacy corpus label, not an established name for a lifetime diagnostic interface on helium HDDs.
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Helium-filled HDD
A helium-filled HDD is a hard disk drive whose head-disk assembly operates in a sealed helium atmosphere to reduce aerodynamic loading.
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Hinted handoff
Hinted handoff retains information about an update missed by an intended replica and attempts to deliver it later.
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Hole punching
Deallocating whole filesystem blocks within a file range while preserving the file's logical length and making the affected range read as zeros.
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Holographic data storage
Stores pages of data as interference patterns in a photosensitive volume, mostly experimental commercially.
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Host bus adapter (HBA)
A host bus adapter (HBA) is the hardware bridge between a server's internal I/O bus (for example PCI Express) and a storage transport such as SCSI, SAS, SATA or Fibre Channel: it contains the initiator ports that send commands to the storage devices (targets).
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Host memory buffer (HMB)
Host Memory Buffer is an optional NVMe feature through which a controller uses assigned host-memory ranges.
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Host-aware SMR
A historical SMR disk interface that exposes zone information while accepting non-sequential writes in sequential-write-preferred zones.
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Host-managed band (SMR)
In host-managed shingled magnetic recording, the host (not the drive) tracks which sequentially written bands are full or empty and must write each one strictly at its write pointer; the standards call these bands zones, and the strict kind is the sequential write required zone of a host-managed zoned block device.
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Host-managed SMR (HM-SMR)
An SMR disk interface that requires writes in sequential-write-required zones to begin at the zone write pointer.
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Host-side flash GC
Host-side flash garbage collection is the reclamation of free space by host software, such as a log-structured file system, a host-based FTL or an application, which copies still-valid data out of a victim region and then explicitly resets or erases that region instead of leaving the work to the SSD's internal FTL.
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Hot journal
A hot journal is a SQLite rollback journal that requires replay to recover an interrupted database transaction.
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Hot standby feedback
Hot standby feedback is PostgreSQL's mechanism for reporting standby query retention needs upstream to defer conflicting row cleanup.
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Hot storage tier
A hot storage tier holds data that is requested frequently and must be served with low latency, on media and with a layout chosen for I/O operations per second rather than storage efficiency; in a published large-scale blob-storage study, content under one day old received more than 100 times the request rate of one-year-old content.
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Hot, warm, and cold storage tiers
A data-placement model where hot tiers favor latency, warm tiers favor cost per TB on disk, and cold tiers favor tape or archive media.
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Hot/cold data separation
A flash-placement strategy that groups data by update frequency so frequently overwritten pages and long-lived pages need not share the same cleaning pool.
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Hybrid flash array
A hybrid flash array is a storage system that combines flash devices with hard-disk capacity pools and uses caching or tiering software to keep frequently accessed data on flash while most of the data stays on disks.
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I/O fencing
I/O fencing enforces exclusion of a node from shared storage so that recovery cannot be undermined by its continued access.
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I/O request size
I/O request size is the number of bytes requested by one input/output operation at a specified system boundary.
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I/O timeout
An I/O timeout is expiration of a layer's waiting limit for an operation, which can trigger recovery without proving that the operation never executed.
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IBM RAMAC
RAMAC (Random Access Method of Accounting and Control) was the first commercial moving-head disk storage product: a stack of fifty 24-inch disks with air-bearing heads, delivered in 1956 as the storage unit of the 305 RAMAC accounting system, giving random access to about 5 million characters (3.75 MB equivalent) where earlier systems used cards, tape or drums.