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<span>Types</span> </div> </a> <button aria-controls="toc-Types-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Types subsection</span> </button> <ul id="toc-Types-sublist" class="vector-toc-list"> <li id="toc-No_wear_leveling" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#No_wear_leveling"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>No wear leveling</span> </div> </a> <ul id="toc-No_wear_leveling-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Dynamic_wear_leveling" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Dynamic_wear_leveling"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Dynamic wear leveling</span> </div> </a> <ul id="toc-Dynamic_wear_leveling-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Static_wear_leveling" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Static_wear_leveling"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>Static wear leveling</span> </div> </a> <ul id="toc-Static_wear_leveling-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Global_wear_leveling" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Global_wear_leveling"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4</span> <span>Global wear leveling</span> </div> </a> <ul id="toc-Global_wear_leveling-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Comparison" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Comparison"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.5</span> <span>Comparison</span> </div> </a> <ul id="toc-Comparison-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Techniques" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Techniques"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Techniques</span> </div> </a> <ul id="toc-Techniques-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item 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class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Operating principle for certain storage media</div> <p><b>Wear leveling</b> (also written as <b>wear levelling</b>) is a technique<sup id="cite_ref-Fundamental_Patent_1-0" class="reference"><a href="#cite_note-Fundamental_Patent-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> for prolonging the <a href="/wiki/Service_life" title="Service life">service life</a> of some kinds of erasable <a href="/wiki/Computer_storage" class="mw-redirect" title="Computer storage">computer storage</a> media, such as <a href="/wiki/Flash_memory" title="Flash memory">flash memory</a>, which is used in <a href="/wiki/Solid-state_drive" title="Solid-state drive">solid-state drives</a> (SSDs) and <a href="/wiki/USB_flash_drive" title="USB flash drive">USB flash drives</a>, and <a href="/wiki/Phase-change_memory" title="Phase-change memory">phase-change memory</a>. There are several wear leveling mechanisms that provide varying levels of longevity enhancement in such memory systems.<sup id="cite_ref-Spansion_2-0" class="reference"><a href="#cite_note-Spansion-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Corsair_3-0" class="reference"><a href="#cite_note-Corsair-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>The term <i>preemptive wear leveling</i> (PWL) has been used by <a href="/wiki/Western_Digital" title="Western Digital">Western Digital</a> to describe their preservation technique used on <a href="/wiki/Hard_disk_drive" title="Hard disk drive">hard disk drives</a> (HDDs) designed for storing audio and video data.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> However, HDDs generally are not wear-leveled devices in the context of this article. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Rationale"><span class="anchor" id="ERASE-BLOCK"></span>Rationale</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=1" title="Edit section: Rationale"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/EEPROM" title="EEPROM">EEPROM</a> and flash memory media have individually erasable segments, each of which can be put through a limited number of erase cycles before becoming unreliable. This is usually around 3,000/5,000 cycles<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> but many flash devices have one block with a specially extended life of 100,000+ cycles that can be used by the <a href="/wiki/Flash_memory_controller" title="Flash memory controller">Flash memory controller</a> to track wear and movement of data across segments. Erasable <a href="/wiki/Optical_disc" title="Optical disc">optical media</a> such as <a href="/wiki/CD-RW" title="CD-RW">CD-RW</a> and <a href="/wiki/DVD-RW" class="mw-redirect" title="DVD-RW">DVD-RW</a> are rated at up to 1,000 cycles (100,000 cycles for <a href="/wiki/DVD-RAM" title="DVD-RAM">DVD-RAM</a> media). </p><p>Wear leveling attempts to work around these limitations by arranging data so that erasures and re-writes are distributed evenly across the medium. In this way, no single erase block prematurely fails due to a high concentration of write cycles.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> In flash memory, a single block on the chip is designed for longer life than the others so that the memory controller can store operational data with less chance of its corruption.<sup id="cite_ref-Corsair_3-1" class="reference"><a href="#cite_note-Corsair-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>Conventional <a href="/wiki/File_system" title="File system">file systems</a> such as <a href="/wiki/File_Allocation_Table" title="File Allocation Table">FAT</a>, <a href="/wiki/Unix_File_System" title="Unix File System">UFS</a>, <a href="/wiki/Hierarchical_File_System_(Apple)" title="Hierarchical File System (Apple)">HFS</a>/<a href="/wiki/HFS_Plus" title="HFS Plus">HFS+</a>, <a href="/wiki/Extended_file_system" title="Extended file system">EXT</a>, and <a href="/wiki/NTFS" title="NTFS">NTFS</a> were originally designed for magnetic disks and as such rewrite many of their data structures (such as their directories) repeatedly to the same area. When these systems are used on flash memory media, this becomes a problem. The problem is aggravated by the fact that some file systems track last-access times, which can lead to file <a href="/wiki/Metadata" title="Metadata">metadata</a> being constantly rewritten in-place.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Types">Types</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=2" title="Edit section: Types"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>There are three basic types of wear leveling mechanisms used in flash memory storage devices:<sup id="cite_ref-Spansion_2-1" class="reference"><a href="#cite_note-Spansion-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="No_wear_leveling">No wear leveling</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=3" title="Edit section: No wear leveling"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A flash memory storage system with <i>no wear leveling</i> will not last very long if data is written to the flash. Without wear leveling, the underlying flash controller must permanently assign the logical addresses from the <a href="/wiki/Operating_system" title="Operating system">operating system</a> (OS) to the physical addresses of the flash memory. This means that every write to a previously written block must first be read, erased, modified, and re-written to the same location. This approach is very time-consuming and frequently written locations will wear out quickly, while other locations will not be used at all. Once a few blocks reach their end of life, such a device becomes inoperable.<sup id="cite_ref-Spansion_2-2" class="reference"><a href="#cite_note-Spansion-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Dynamic_wear_leveling">Dynamic wear leveling</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=4" title="Edit section: Dynamic wear leveling"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The first type of wear leveling is called <i>dynamic wear leveling</i> and it uses a map to link <a href="/wiki/Logical_block_address" class="mw-redirect" title="Logical block address">logical block addresses</a> (LBAs) from the OS to the physical flash memory. Each time the OS writes replacement data, the map is updated so the original physical block is marked as <i>invalid</i> data, and a new block is linked to that map entry. Each time a block of data is re-written to the flash memory, it is written to a new location. However, flash memory blocks that never get replacement data would sustain no additional wear, thus the name comes only from the dynamic data being recycled. Such a device may last longer than one with no wear leveling, but there are blocks still remaining as active even though the device is no longer operable.<sup id="cite_ref-Spansion_2-3" class="reference"><a href="#cite_note-Spansion-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Corsair_3-2" class="reference"><a href="#cite_note-Corsair-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Static_wear_leveling">Static wear leveling</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=5" title="Edit section: Static wear leveling"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The other type of wear leveling is called <i>static wear leveling</i> which also uses a map to link the LBA to physical memory addresses. Static wear leveling works the same as dynamic wear leveling except the static blocks that do not change are periodically moved so that these low usage cells are able to be used by other data. This rotational effect enables an SSD to continue to operate until most of the blocks are near their end of life.<sup id="cite_ref-Spansion_2-4" class="reference"><a href="#cite_note-Spansion-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Corsair_3-3" class="reference"><a href="#cite_note-Corsair-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Global_wear_leveling">Global wear leveling</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=6" title="Edit section: Global wear leveling"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Both dynamic and static wear leveling are implemented at the local level. This simply means that in a multi-chip product, every chip is managed as a single resource. The number of defective blocks in different chips within a NAND flash memory varies: a given chip could have all its data blocks worn out while another chip in the same device could have all its blocks still active. Global wear leveling addresses this problem by managing all blocks from all chips in the flash memory together―in a single pool. It ensures that all the cells in all the chips within the product are worn out evenly. <sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Comparison">Comparison</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=7" title="Edit section: Comparison"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The following table compares static and dynamic wear leveling:<sup id="cite_ref-Corsair_3-4" class="reference"><a href="#cite_note-Corsair-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable sortable"> <tbody><tr> <th>Item </th> <th>Static </th> <th>Dynamic </th></tr> <tr> <td><a href="/wiki/Endurance" title="Endurance">Endurance</a> </td> <td>Longer life expectancy </td> <td>Shorter life expectancy </td></tr> <tr> <td>Performance </td> <td>Slower </td> <td>Faster </td></tr> <tr> <td>Design complexity </td> <td>More complex </td> <td>Less complex </td></tr> <tr> <td>Typical use </td> <td>SSDs,<sup id="cite_ref-Spansion_2-5" class="reference"><a href="#cite_note-Spansion-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> <br />industrial-grade flash drives<sup id="cite_ref-:0_12-0" class="reference"><a href="#cite_note-:0-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </td> <td>Consumer-grade flash drives </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Techniques">Techniques</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=8" title="Edit section: Techniques"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>There are several techniques for extending the media life: </p> <ul><li>A checksum or <a href="/wiki/Error_detection_and_correction" title="Error detection and correction">error-correcting</a> code can be kept for each block or sector in order to detect errors or correct errors.</li> <li>A pool of <a href="/wiki/Overprovisioning" title="Overprovisioning">overprovisioned</a> reserve space can also be kept. When a block or sector does fail, future reads and writes to it can be redirected to a replacement in that pool.</li> <li>Blocks or sectors on the media can be tracked in a <a href="/wiki/Least_frequently_used" title="Least frequently used">least frequently used</a> (LFU) queue. The data structures for the queue itself must either be stored off-device or in such a way that the space it uses is itself wear-leveled or, in the case of flash memory, in a block with a specially extended life. However, usual <a href="/wiki/Cache_algorithms" class="mw-redirect" title="Cache algorithms">cache algorithms</a> are designed to manage the data flow into and out of <a href="/wiki/Random-access_memory" title="Random-access memory">RAM</a>-based caches, making them not directly suitable for <a href="/wiki/Flash_memory" title="Flash memory">flash-based</a> storage devices as they have an asymmetrical nature –  reads are usually much faster than writes, and erase operations can be performed only one "block" at a time.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Garbage_collection_(SSD)" class="mw-redirect" title="Garbage collection (SSD)">Garbage collection</a></li></ul> <p>On <a href="/wiki/Secure_Digital_card" class="mw-redirect" title="Secure Digital card">Secure Digital cards</a> and <a href="/wiki/USB_flash_drive" title="USB flash drive">USB flash drives</a>,<sup id="cite_ref-:0_12-1" class="reference"><a href="#cite_note-:0-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> techniques are implemented in hardware by a built-in <a href="/wiki/Microcontroller" title="Microcontroller">microcontroller</a>. On such devices, wear leveling is <a href="/wiki/Transparency_(human-computer_interaction)" class="mw-redirect" title="Transparency (human-computer interaction)">transparent</a>, and conventional file system such as <a href="/wiki/File_Allocation_Table" title="File Allocation Table">FAT</a> can be used on them as-is. </p><p>Wear leveling can also be implemented in software by special-purpose file systems such as <a href="/wiki/JFFS2" title="JFFS2">JFFS2</a> and <a href="/wiki/YAFFS" title="YAFFS">YAFFS</a> on flash media or <a href="/wiki/Universal_Disk_Format" title="Universal Disk Format">UDF</a> on optical media. All three are <a href="/wiki/Log-structured_file_system" title="Log-structured file system">log-structured file systems</a> in that they treat their media as circular logs and write to them in sequential passes. File systems which implement <a href="/wiki/Copy-on-write" title="Copy-on-write">copy-on-write</a> strategies, such as <a href="/wiki/ZFS" title="ZFS">ZFS</a>, also implement a form of wear leveling. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=9" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Flash_file_system" title="Flash file system">Flash file system</a></li> <li><a href="/wiki/Battery_balancing" title="Battery balancing">Battery balancing</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=10" title="Edit section: References"><span>edit</span></a><span 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Toledo, ACM Computing Surveys, 2005</span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFArnd_Bergmann2011" class="citation web cs1">Arnd Bergmann (2011-02-18). <a rel="nofollow" class="external text" href="https://lwn.net/Articles/428584/">"Optimizing Linux with cheap flash drives"</a>. <a href="/wiki/LWN.net" title="LWN.net">LWN.net</a><span class="reference-accessdate">. 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Retrieved <span class="nowrap">2014-01-21</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Once+upon+atime&rft.pub=LWN.net&rft.date=2007-08-08&rft.au=Jonathan+Corbet&rft_id=https%3A%2F%2Flwn.net%2FArticles%2F244829%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWear+leveling" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.transcend-info.com/Embedded/Essay-22">"Wear Leveling"</a>. <i>Transcend</i><span class="reference-accessdate">. Retrieved <span class="nowrap">20 November</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Transcend&rft.atitle=Wear+Leveling&rft_id=https%3A%2F%2Fwww.transcend-info.com%2FEmbedded%2FEssay-22&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWear+leveling" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation journal cs1"><a rel="nofollow" class="external text" href="https://www.cactus-tech.com/wp-content/uploads/2019/03/Wear-Leveling-Static-Dynamic-Global.pdf">"Wear Leveling – Static, Dynamic and Global"</a> <span class="cs1-format">(PDF)</span>. <i>Cactus</i>: 5<span class="reference-accessdate">. Retrieved <span class="nowrap">20 November</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Cactus&rft.atitle=Wear+Leveling+%E2%80%93+Static%2C+Dynamic+and+Global&rft.pages=5&rft_id=https%3A%2F%2Fwww.cactus-tech.com%2Fwp-content%2Fuploads%2F2019%2F03%2FWear-Leveling-Static-Dynamic-Global.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWear+leveling" class="Z3988"></span></span> </li> <li id="cite_note-:0-12"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_12-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_12-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://eu.mouser.com/new/Swissbit/swissbit-industrial-SD-memory/">"Swissbit Industrial SD Memory Cards"</a>. <a href="/wiki/Mouser_Electronics" title="Mouser Electronics">Mouser Electronics</a><span class="reference-accessdate">. Retrieved <span class="nowrap">21 April</span> 2017</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Swissbit+Industrial+SD+Memory+Cards&rft.pub=Mouser+Electronics&rft_id=http%3A%2F%2Feu.mouser.com%2Fnew%2FSwissbit%2Fswissbit-industrial-SD-memory%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWear+leveling" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFQing_Yang2012" class="citation web cs1">Qing Yang (2012-02-25). <a rel="nofollow" class="external text" href="http://www.velobit.com/storage-performance-blog/bid/118134/Why-Standard-Cache-Algorithms-Won-t-Work-For-SSDs">"Why Standard Cache Algorithms Won't Work For SSDs"</a>. velobit.com<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-11-26</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Why+Standard+Cache+Algorithms+Won%27t+Work+For+SSDs&rft.pub=velobit.com&rft.date=2012-02-25&rft.au=Qing+Yang&rft_id=http%3A%2F%2Fwww.velobit.com%2Fstorage-performance-blog%2Fbid%2F118134%2FWhy-Standard-Cache-Algorithms-Won-t-Work-For-SSDs&rfr_id=info%3Asid%2Fen.wikipedia.org%3AWear+leveling" class="Z3988"></span></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wear_leveling&action=edit&section=11" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070202230957/http://www.bitmicro.com/press_resources_flash_ssd.php">Flash SSDs –  Inferior Technology or Closet Superstar?</a>, bitmicro.com, archived from the original on February 2, 2007</li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist 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style="font-size:114%;margin:0 4em"><a href="/wiki/Solid-state_drive" title="Solid-state drive">Solid-state drives</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Key terminology</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Encryption" title="Encryption">Encryption</a></li> <li><a href="/wiki/Error_detection_and_correction" title="Error detection and correction">ECC</a></li> <li><a href="/wiki/Flash_file_system" title="Flash file system">Flash file system</a></li> <li><a href="/wiki/Flash_memory" title="Flash memory">Flash memory</a></li> <li><a href="/wiki/Multi-level_cell" title="Multi-level cell">SLC/MLC</a></li> <li><a href="/wiki/Flash_memory_controller" title="Flash memory controller">Flash memory controller</a></li> <li><a href="/wiki/Garbage_collection_(SSD)" class="mw-redirect" title="Garbage collection (SSD)">Garbage collection</a></li> <li><a href="/wiki/IOPS" title="IOPS">IOPS</a></li> <li><a href="/wiki/Bit_rate" title="Bit rate">MB/s</a></li> <li><a href="/wiki/Flash_memory#Memory_wear" title="Flash memory">Memory wear</a></li> <li><a href="/wiki/Open-channel_SSD" title="Open-channel SSD">Open-channel SSD</a></li> <li><a href="/wiki/Write_amplification#Over-provisioning" title="Write amplification">Over-provisioning</a></li> <li><a href="/wiki/Flash_memory#Read_disturb" title="Flash memory">Read disturb</a></li> <li><a href="/wiki/Write_amplification#Secure_erase" title="Write amplification">Secure erase</a></li> <li><a href="/wiki/Solid-state_storage" title="Solid-state storage">Solid-state storage</a></li> <li><a href="/wiki/Trim_(computing)" title="Trim (computing)">Trim command</a></li> <li><a class="mw-selflink selflink">Wear leveling</a></li> <li><a href="/wiki/Write_amplification" title="Write amplification">Write amplification</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Flash manufacturers</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Micron_Technology" title="Micron Technology">Micron</a></li> <li><a href="/wiki/Samsung_Electronics" title="Samsung Electronics">Samsung</a></li> <li><a href="/wiki/SK_Hynix" title="SK Hynix">SK Hynix</a> <ul><li>Bought <a href="/wiki/Intel" title="Intel">Intel</a>'s NAND flash SSD business and renamed it Solidigm</li></ul></li> <li>Flash Forward (joint venture between <a href="/wiki/Western_Digital" title="Western Digital">Western Digital</a> and <a href="/wiki/Kioxia" title="Kioxia">Kioxia</a>)</li> <li><a href="/wiki/Yangtze_Memory_Technologies" title="Yangtze Memory Technologies">YMTC</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_flash_memory_controller_manufacturers" title="List of flash memory controller manufacturers">Controllers</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Captive</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Western_Digital" title="Western Digital">Western Digital</a> <ul><li><a href="/wiki/SanDisk" title="SanDisk">SanDisk</a></li> <li><a href="/wiki/Fusion-io" title="Fusion-io">Fusion-io</a></li> <li><a href="/wiki/HGST" title="HGST">HGST</a></li> <li><a href="/wiki/STec" title="STec">sTec</a></li></ul></li> <li><a href="/wiki/Kioxia" title="Kioxia">Kioxia</a> <ul><li><a href="/wiki/OCZ" title="OCZ">OCZ</a> (bankrupt, assets sold to Toshiba, which later spun off its SSD and flash business to Kioxia)</li> <li><a href="/wiki/Indilinx" title="Indilinx">Indilinx</a> (bought by OCZ)</li></ul></li> <li><a href="/wiki/Micron_Technology" title="Micron Technology">Micron</a></li> <li><a href="/wiki/Samsung_Electronics" title="Samsung Electronics">Samsung</a></li> <li><a href="/wiki/Seagate_Technology" title="Seagate Technology">Seagate</a> <ul><li><a href="/wiki/SandForce" title="SandForce">SandForce</a></li></ul></li> <li><a href="/wiki/SK_Hynix" title="SK Hynix">SK Hynix</a> <ul><li>Bought <a href="/wiki/Intel" title="Intel">Intel</a>'s NAND flash SSD business including controllers and renamed it Solidigm</li></ul></li> <li><a href="/w/index.php?title=FADU&action=edit&redlink=1" class="new" title="FADU (page does not exist)">FADU</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Independent</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Greenliant_Systems" title="Greenliant Systems">Greenliant Systems</a></li> <li><a href="/w/index.php?title=Goke_Microelectronics&action=edit&redlink=1" class="new" title="Goke Microelectronics (page does not exist)">Goke</a></li> <li><a href="/wiki/JMicron" title="JMicron">Maxiotek</a></li> <li><a href="/wiki/Marvell_Technology_Group" class="mw-redirect" title="Marvell Technology Group">Marvell</a></li> <li><a href="/wiki/Phison" title="Phison">Phison</a></li> <li><a href="/wiki/PMC-Sierra" title="PMC-Sierra">PMC-Sierra</a></li> <li><a href="/wiki/Silicon_Motion" title="Silicon Motion">SMI</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">SSD manufacturers</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/List_of_solid-state_drive_manufacturers" title="List of solid-state drive manufacturers">List of solid-state drive manufacturers</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Interfaces</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Advanced_Host_Controller_Interface" title="Advanced Host Controller Interface">Advanced Host Controller Interface</a> (AHCI)</li> <li><a href="/wiki/Fibre_Channel" title="Fibre Channel">Fibre Channel</a> (FC)</li> <li><a href="/wiki/NVM_Express" title="NVM Express">NVM Express</a> (NVMe)</li> <li><a href="/wiki/PCI_Express" title="PCI Express">PCI Express</a> (PCIe)</li> <li><a href="/wiki/SATA_Express" title="SATA Express">SATA Express</a></li> <li><a href="/wiki/Serial_ATA" class="mw-redirect" title="Serial ATA">Serial ATA</a> (SATA)</li> <li><a href="/wiki/Serial_attached_SCSI" class="mw-redirect" title="Serial attached SCSI">Serial attached SCSI</a> (SAS)</li> <li><a href="/wiki/USB" title="USB">Universal Serial Bus</a> (USB)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Configurations</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Hard_disk_drive#Form_factors" title="Hard disk drive">HDD form factors</a></li> <li><a href="/wiki/MSATA" class="mw-redirect" title="MSATA">mSATA</a></li> <li><a href="/wiki/M.2" title="M.2">M.2</a></li> <li><a href="/wiki/PCI_Express" title="PCI Express">PCI Express</a> <a href="/wiki/Expansion_card" title="Expansion card">expansion card</a></li> <li><a href="/wiki/Thunderbolt_(interface)" title="Thunderbolt (interface)">Thunderbolt</a> <ul><li><a href="/wiki/USB-C" title="USB-C">USB Type-C</a></li></ul></li> <li><a href="/wiki/U.2" title="U.2">U.2</a></li> <li><a href="/wiki/U.3" class="mw-redirect" title="U.3">U.3</a></li> <li><a href="/wiki/EDSFF" class="mw-redirect" title="EDSFF">EDSFF</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related organizations</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/International_Committee_for_Information_Technology_Standards" title="International Committee for Information Technology Standards">INCITS</a></li> <li><a href="/wiki/JEDEC" title="JEDEC">JEDEC / JC-42, JC-64.8</a></li> <li><a href="/wiki/Open_NAND_Flash_Interface_Working_Group" title="Open NAND Flash Interface Working Group">ONFI</a></li> <li><a href="/wiki/NVM_Express#History" title="NVM Express">NVMHCI Work Group</a></li> <li><a href="/wiki/USB_Implementers_Forum" title="USB Implementers Forum">USB-IF</a></li> <li><a href="/wiki/Serial_ATA_International_Organization" title="Serial ATA International Organization">SATA-IO</a></li> <li><a href="/wiki/Small_Form_Factor_Committee" title="Small Form Factor Committee">SFF Committee</a></li> <li><a href="/wiki/Storage_Networking_Industry_Association" title="Storage Networking Industry Association">SNIA</a></li> <li><a href="/wiki/Solid_state_storage_initiative" class="mw-redirect" title="Solid state storage initiative">SSSI</a></li> <li><a href="/wiki/SCSI" title="SCSI">T10/SCSI</a></li> <li><a href="/wiki/Fibre_Channel" title="Fibre Channel">T11/FC</a></li> <li><a href="/wiki/Parallel_ATA" title="Parallel ATA">T13/ATA</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <b><a href="/wiki/Category:Solid-state_computer_storage" title="Category:Solid-state computer storage">Category</a></b></li></ul> </div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Wear_leveling&oldid=1256242801">https://en.wikipedia.org/w/index.php?title=Wear_leveling&oldid=1256242801</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Computer_memory" title="Category:Computer memory">Computer memory</a></li><li><a href="/wiki/Category:Non-volatile_memory" title="Category:Non-volatile memory">Non-volatile memory</a></li><li><a href="/wiki/Category:Flash_file_systems" title="Category:Flash file systems">Flash file systems</a></li><li><a href="/wiki/Category:Solid-state_computer_storage" title="Category:Solid-state computer storage">Solid-state computer storage</a></li><li><a href="/wiki/Category:Balancing_technology" title="Category:Balancing technology">Balancing technology</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li></ul></div></div> </div> </main> </div> 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