--- title: Hard drives quietly changed how they write data, and... description: Hard drives use one of two recording methods: CMR (Conventional Magnetic Recording), which writes data on non-overlapping tracks, or SMR (Shingled Magnetic... canonical: https://daily.dev/posts/hard-drives-quietly-changed-how-they-write-data-and-it-s-why-some-of-them-are-awful-in-your-nas-qef0fzqee twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Hard drives quietly changed how they write data, and it's why some of them are awful in your NAS | daily.dev og:description: Hard drives use one of two recording methods: CMR (Conventional Magnetic Recording), which writes data on non-overlapping tracks, or SMR (Shingled Magnetic... og:url: https://daily.dev/posts/hard-drives-quietly-changed-how-they-write-data-and-it-s-why-some-of-them-are-awful-in-your-nas-qef0fzqee og:image: https://api.daily.dev/og/posts/qef0FZQEe.png og:image:alt: Hard drives quietly changed how they write data, and it's why some of them are awful in your NAS og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Hard drives quietly changed how they write data, and it's why some of them are awful in your NAS **[XDA Developers](https://daily.dev/sources/xda-developers)** · 3 min read · 0 upvotes · 0 comments ## Summary Hard drives use one of two recording methods: CMR (Conventional Magnetic Recording), which writes data on non-overlapping tracks, or SMR (Shingled Magnetic Recording), introduced quietly around 2013, which overlaps tracks to boost density by up to 25% and lower cost. SMR drives struggle with sustained, write-heavy workloads and complex RAID setups, making them a poor fit for NAS systems handling backups or multi-user syncing. NAS-branded drives like WD Red Plus/Pro and Seagate IronWolf use CMR along with tuned firmware and higher reliability. SMR drives remain a good cost-effective choice for write-once-read-many scenarios like archival storage, media libraries, and cold storage. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is the difference between CMR and SMR hard drives? CMR (Conventional Magnetic Recording) writes data on non-overlapping, side-by-side tracks, so each track is independent. SMR (Shingled Magnetic Recording) overlaps adjacent tracks like roof shingles, packing up to 25% more data into the same space and lowering cost, but at the expense of sustained write performance. _Comparing drive types before a NAS build is easier with daily.dev's coverage of storage hardware._ ### Why are SMR hard drives bad for NAS and RAID setups? SMR drives struggle with write-heavy workloads because their overlapping track design makes rewriting data slower and more complex than on CMR drives. NAS systems that handle constant backups, small random writes, multiple users syncing data, or RAID rebuilds can suffer performance problems and instability with SMR drives, especially during RAID resilvering. _Anyone planning a reliable NAS RAID setup can track storage hardware pitfalls via daily.dev._ ### When is it okay to use SMR hard drives instead of CMR? SMR drives work fine for write once, read many (WORM) use cases such as archival data, media libraries, older backups, and cold storage where sustained write performance isn't required. They cost less than CMR drives, especially at larger capacities, making them a reasonable choice when a NAS won't see heavy, continuous write activity. _Weighing storage cost against workload demands is easier by following hardware buying guides on daily.dev._ ## Similar posts on daily.dev - [One in four HDDs fail without any warning, and your NAS won't be able to tell you](https://daily.dev/posts/one-in-four-hdds-fail-without-any-warning-and-your-nas-won-t-be-able-to-tell-you-eaf0xklfb) · XDA Developers · 0 upvotes · 0 comments - [I found a free tool that shows real NAS drive failure rates, and it changed the way I buy storage](https://daily.dev/posts/i-found-a-free-tool-that-shows-real-nas-drive-failure-rates-and-it-changed-the-way-i-buy-storage-fkcyp3yvi) · XDA Developers · 0 upvotes · 0 comments - [My NAS corrupted years of files because I ignored three critical setup mistakes](https://daily.dev/posts/my-nas-corrupted-years-of-files-because-i-ignored-three-critical-setup-mistakes-yx7b75ced) · XDA Developers · 0 upvotes · 0 comments --- Tags: [#storage](https://daily.dev/tags/storage) [View this post on daily.dev](https://daily.dev/posts/hard-drives-quietly-changed-how-they-write-data-and-it-s-why-some-of-them-are-awful-in-your-nas-qef0fzqee) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Hard drives quietly changed how they write data, and it's why some of them are awful in your NAS","url":"https://daily.dev/posts/hard-drives-quietly-changed-how-they-write-data-and-it-s-why-some-of-them-are-awful-in-your-nas-qef0fzqee","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/hard-drives-quietly-changed-how-they-write-data-and-it-s-why-some-of-them-are-awful-in-your-nas-qef0fzqee"},"datePublished":"2026-08-15T20:32:10.538Z","dateModified":"2026-08-15T20:32:42.525Z","description":"Hard drives use one of two recording methods: CMR (Conventional Magnetic Recording), which writes data on non-overlapping tracks, or SMR (Shingled Magnetic...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/b36aeedb507b3be7a0c22ed1d6183d70?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/b36aeedb507b3be7a0c22ed1d6183d70?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"XDA Developers","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"XDA Developers","logo":"https://media.daily.dev/image/upload/s--kCg6yyAP--/f_auto,q_auto/v1774964407/logos/xda-developers?_a=BAMAMiWQ0","url":"https://daily.dev/sources/xda-developers"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/hard-drives-quietly-changed-how-they-write-data-and-it-s-why-some-of-them-are-awful-in-your-nas-qef0fzqee","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"storage","timeRequired":"PT3M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"XDA Developers","item":"https://daily.dev/sources/xda-developers"},{"@type":"ListItem","position":3,"name":"Hard drives quietly changed how they write data, and it's why some of them are awful in your NAS"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/hard-drives-quietly-changed-how-they-write-data-and-it-s-why-some-of-them-are-awful-in-your-nas-qef0fzqee#faq","mainEntity":[{"@type":"Question","name":"What is the difference between CMR and SMR hard drives?","acceptedAnswer":{"@type":"Answer","text":"CMR (Conventional Magnetic Recording) writes data on non-overlapping, side-by-side tracks, so each track is independent. 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