--- title: All Your GUCs in a Row: file_copy_method | daily.dev description: PostgreSQL 18 introduces the `file_copy_method` GUC with a `clone` option that leverages copy-on-write filesystem reflinks to make `CREATE DATABASE` nearly... canonical: https://daily.dev/posts/all-your-gucs-in-a-row-file-copy-method-plrdeoars twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: All Your GUCs in a Row: file_copy_method | daily.dev og:description: PostgreSQL 18 introduces the `file_copy_method` GUC with a `clone` option that leverages copy-on-write filesystem reflinks to make `CREATE DATABASE` nearly... og:url: https://daily.dev/posts/all-your-gucs-in-a-row-file-copy-method-plrdeoars og:image: https://api.daily.dev/og/posts/pLrDeOaRs.png og:image:alt: All Your GUCs in a Row: file_copy_method 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. # All Your GUCs in a Row: file_copy_method **[Planet PostgreSQL](https://daily.dev/sources/planet-postgresql)** · 3 min read · 1 upvotes · 0 comments ## Summary PostgreSQL 18 introduces the `file_copy_method` GUC with a `clone` option that leverages copy-on-write filesystem reflinks to make `CREATE DATABASE` nearly instantaneous regardless of database size. On supported filesystems (XFS with reflinks, Btrfs, ZFS, APFS), cloning a 120 GB database takes ~200ms and an 800 GB one under a second. Three preconditions must all be met: a COW-capable filesystem, explicitly requesting `STRATEGY = FILE_COPY`, and no active sessions on the template database. The default `copy` setting does a full byte-for-byte duplication, while `clone` only writes metadata pointers. This makes per-branch and per-developer throwaway databases practical. On non-COW filesystems like ext4, `clone` fails rather than falling back silently. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What does file_copy_method = clone do in PostgreSQL 18? It changes CREATE DATABASE (with STRATEGY = FILE_COPY) and ALTER DATABASE ... SET TABLESPACE to use OS-level reflinking instead of a byte-for-byte copy, calling copy_file_range() on Linux or copyfile() on macOS. On copy-on-write filesystems this shares blocks via metadata pointers rather than duplicating data, making the copy nearly instant regardless of database size. _daily.dev surfaces practical PostgreSQL tuning changes like this for engineers optimizing database provisioning workflows._ ### Which filesystems support PostgreSQL's file_copy_method clone setting? It requires a copy-on-write filesystem: XFS with reflinks enabled (the default in modern XFS), Btrfs, ZFS, or APFS. On ext4 there is no reflink support, so clone fails outright rather than silently falling back to a regular copy, which matters inside container images that default to ext4. _Teams choosing storage backends for PostgreSQL can track filesystem compatibility notes like this via daily.dev._ ### How fast is cloning a PostgreSQL database with file_copy_method = clone versus a regular copy? Cloning a 120GB database takes around 200 milliseconds and an 800GB database just over half a second, since copy-on-write reflinking only writes new metadata pointers rather than moving data. This makes CREATE DATABASE near-instant on supported filesystems, compared to the default copy method, which duplicates every byte and scales with database size. _daily.dev helps engineers weighing database provisioning speed keep up with PostgreSQL performance changes like this._ ## Similar posts on daily.dev - [3 Hours to 7 Minutes: Fixing Aurora PostgreSQL’s Silent CREATE DATABASE Regression](https://daily.dev/posts/3-hours-to-7-minutes-fixing-aurora-postgresql-s-silent-create-database-regression-ea1iig0ij) · Medium · 0 upvotes · 0 comments - [All Your GUCs in a Row: file\_extend\_method](https://daily.dev/posts/all-your-gucs-in-a-row-file-extend-method-2xigzvfm6) · Planet PostgreSQL · 1 upvotes · 1 comments --- Tags: [#postgresql](https://daily.dev/tags/postgresql) [View this post on daily.dev](https://daily.dev/posts/all-your-gucs-in-a-row-file-copy-method-plrdeoars) ```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":"All Your GUCs in a Row: file_copy_method","url":"https://daily.dev/posts/all-your-gucs-in-a-row-file-copy-method-plrdeoars","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/all-your-gucs-in-a-row-file-copy-method-plrdeoars"},"datePublished":"2026-07-21T01:05:35.091Z","dateModified":"2026-09-13T20:54:35.578Z","description":"PostgreSQL 18 introduces the `file_copy_method` GUC with a `clone` option that leverages copy-on-write filesystem reflinks to make `CREATE DATABASE` nearly...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/cc492a393909b40f5641e6bf814a7729?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/cc492a393909b40f5641e6bf814a7729?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Planet PostgreSQL","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":"Planet PostgreSQL","logo":"https://media.daily.dev/image/upload/logos/placeholder.jpg","url":"https://daily.dev/sources/planet-postgresql"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/all-your-gucs-in-a-row-file-copy-method-plrdeoars","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":1},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"postgresql","timeRequired":"PT3M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Planet PostgreSQL","item":"https://daily.dev/sources/planet-postgresql"},{"@type":"ListItem","position":3,"name":"All Your GUCs in a Row: file_copy_method"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/all-your-gucs-in-a-row-file-copy-method-plrdeoars#faq","mainEntity":[{"@type":"Question","name":"What does file_copy_method = clone do in PostgreSQL 18?","acceptedAnswer":{"@type":"Answer","text":"It changes CREATE DATABASE (with STRATEGY = FILE_COPY) and ALTER DATABASE ... 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