Hesela / Structured knowledge

Storage Knowledge Corpus

Storage definitions, connected to their evidence.

866 terms · Page 27 of 29

A-Z

  1. Term

    Thermal writability

    Thermal writability is the requirement that a magnetic write field bias the intended state strongly enough relative to thermal fluctuations to meet a recording-error target.

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  2. Term

    Thin pool

    In Linux LVM, a shared allocation pool combining separate data and metadata logical volumes to back thin logical volumes and their snapshots.

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  3. Term

    Thin provisioning

    Presenting logical storage capacity while allocating physical backing from a shared pool as writes require it.

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  4. Term

    Thin-pool metadata

    The dm-thin mapping and allocation information stored in a separate logical metadata device to track how thin volumes use a pool's data blocks.

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  5. Term

    Thunderbolt storage

    Thunderbolt storage is external storage, typically an NVMe enclosure, that attaches over a Thunderbolt or USB4 link by tunneling PCIe, so the drive appears to the host as a PCIe device and not as a USB mass-storage device, with access control and DMA protection needed because the device can act as a bus master.

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  6. Term

    Tied request

    A tied request is a duplicate request whose server coordinates with the other copy's server so that starting execution can cancel or deprioritize a still-queued counterpart.

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  7. Term

    Tiered compaction

    Tiered compaction allows multiple sorted runs to accumulate and merges groups of runs into typically larger runs instead of maintaining one run at every tier.

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  8. Term

    Tiled magnetic recording

    A proposed patterning approach grouping grains into magnetic tiles for higher density.

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  9. Term

    TinyLFU

    TinyLFU is a cache admission policy that compares approximate recent access frequencies of a candidate and an eviction victim.

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  10. Term

    TLC SSD

    A TLC SSD uses NAND flash that encodes three bits per cell using eight threshold-voltage states.

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  11. Term

    TMR read head

    A TMR read head senses recorded bits with a magnetic tunnel junction: a free layer and a pinned layer separated by a thin insulating barrier (for example MgO) through which the current tunnels, so the junction resistance changes with the relative magnetization of the two layers.

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  12. Term

    Torn write

    A torn write is an interrupted write that persists only part of its intended update, potentially leaving a database page with mixed old and new contents.

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  13. Term

    Touchdown sensor (TDS)

    An HDD touchdown sensor is a temperature-sensitive element used to observe thermal changes near the head-disk interface during clearance and contact studies.

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  14. Term

    Transition jitter

    Transition jitter is variation in the positions of recorded magnetization reversals relative to their intended or estimated locations.

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  15. Term

    Transparent filesystem compression

    Filesystem-managed compression of eligible file data that preserves the original logical bytes exposed to applications.

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  16. Term

    TRIM

    The ATA DATA SET MANAGEMENT Trim function tells a device that specified logical block ranges are no longer needed.

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  17. Term

    Triple-level cell (TLC)

    NAND flash that stores three bits per cell using eight distinguishable threshold-voltage states.

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  18. Term

    U.2

    U.2 identifies PCIe SSDs and connections compliant with the PCI Express SFF-8639 Module specification, commonly implemented in a 2.5-inch drive enclosure.

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  19. Term

    U.3

    U.3 is the SFF-TA-1001 universal x4 link arrangement for SFF-8639 drive bays that can accommodate PCIe, SAS, or SATA devices with appropriate host support.

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  20. Term

    UASP

    USB Attached SCSI Protocol (UASP) transports SCSI commands over USB and supports multiple outstanding commands, without by itself guaranteeing throughput, SMART pass-through or durable writes.

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  21. Term

    UDO

    Ultra Density Optical (UDO) is a standardised 130 mm two-sided optical disk cartridge using a 405 nm laser and phase-change recording, with rewritable (RW) and write-once (WORM) types; the first generation holds a nominal 30 Gbytes per cartridge (ECMA-350) and the second generation 60 Gbytes (ECMA-380).

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  22. Term

    UFS (Universal Flash Storage)

    UFS is a JEDEC flash-storage specification with a serial interface and a layered architecture using MIPI M-PHY, MIPI UniPro and SCSI command conventions.

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  23. Term

    Uncorrectable bit error rate

    Uncorrectable bit error rate is a storage reliability metric that normalizes unrecovered data-error outcomes by a specified bit count after the stated correction and recovery procedures.

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  24. Term

    Unlink

    Unlink is the removal of a directory entry naming a file; POSIX semantics preserve existing open references, while network-filesystem behavior requires additional qualification.

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  25. Term

    UNMAP

    The SCSI UNMAP command requests deallocation of logical blocks.

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  26. Term

    Unserializable write

    An unserializable write is a storage failure in which recovered contents cannot be reconciled with an operation order allowed by the known write history.

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  27. Term

    Unwritten extent

    An allocated filesystem extent whose data is not initialized and is exposed as zeros when read through the filesystem.

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  28. Term

    Up set (Ceph)

    In Ceph, the up set is the ordered OSD list assigned to a placement group by CRUSH for a particular map epoch.

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  29. Term

    USB mass storage

    The USB device class that presents block storage to hosts using BOT or UASP transports.

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  30. Term

    V-NAND

    V-NAND (vertical NAND) is the trade name one manufacturer uses for its 3D NAND flash, in which memory cells are stacked in dozens of word-line layers on one die instead of being laid out in a single plane.

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