# Pantheon starts moving existing WordPress and Drupal sites off its Valhalla filesystem Pantheon has started migrating existing WordPress and Drupal sites from its long-running Valhalla shared filesystem to Google Cloud Storage FUSE, beginning with Free sites on September 1 and rolling through paid tiers during the rest of 2026. This is a platform architecture migration rather than a user-facing feature. Pantheon says no action is required, but builders operating storage-sensitive WordPress or Drupal workloads should know when their tier moves and verify backup, restore and file-handling behavior around the change. - Status: Active - Published: 2026-09-01T20:39:58+12:00 - Updated: 2026-09-01T20:39:58+12:00 - Categories: Web Development, Cloud & Infrastructure, Hosting, Cloud Platforms, WordPress, Databases & Storage - Tags: Drupal, filesystem migration, Google Cloud Storage FUSE, Pantheon - Canonical HTML: https://beyondthe.news/dossiers/pantheon-existing-sites-valhalla-cloud-storage-fuse-migration-2026 ## What changed Pantheon is replacing the Valhalla shared filesystem it built for horizontally scaled PHP sites with a filesystem backed by Google Cloud Storage FUSE. New sites began moving in August; migrations of existing sites began September 1, 2026. Pantheon lists Free sites first, followed by Basic on October 5, Performance on November 16 and Elite on November 30. The company says the new filesystem improves backup and restore performance and reliability, and that no customer action is required. ## Why it matters For hosted WordPress and Drupal sites, uploaded media and other CMS-managed files sit on the shared storage layer even when application containers scale horizontally. Changing that layer alters a core piece of runtime architecture beneath existing sites. Pantheon says the migration is transparent, but teams with unusual filesystem assumptions, large media libraries, custom backup workflows or integrations that depend on file timing should treat the rollout as an infrastructure event worth observing rather than a cosmetic platform update. ## Valhalla is being replaced beneath existing sites Pantheon created Valhalla to make WordPress and Drupal uploaded files behave like a shared local filesystem across horizontally scaled containers. The company now says Cloud Storage FUSE has surpassed that design for its needs and is becoming the replacement storage layer. ## The existing-site rollout starts with Free plans New sites began receiving the new filesystem in August. Existing sites entered the migration phase on September 1, starting with Free sites. Pantheon plans later waves for Basic, Performance and Elite tiers through November. ## Pantheon says the migration is automatic The release notes do not ask customers to copy files or change application code. Pantheon says no additional action is required and exposes a Filesystem Generation value in Site Details so operators can see whether a site has moved. ## The practical risk is hidden filesystem assumptions Most standard WordPress and Drupal sites should not need changes, but custom code, media-processing jobs, backup tooling and integrations sometimes rely on subtle filesystem behavior. Teams running those patterns should verify them after migration, especially around write visibility, backup/restore behavior and large file sets. ## Key details - Pantheon is deprecating its Valhalla shared filesystem in favor of Google Cloud Storage FUSE. - Existing-site migrations began September 1, 2026. - Free sites migrate first; Basic is scheduled for October 5, Performance for November 16 and Elite for November 30. - Pantheon says no customer action is required for the filesystem migration. - The company says the replacement improves backup and restore speed and reliability. - Site details expose a Filesystem Generation field; generation 2 identifies the new filesystem. ## Builder takeaways - Check the Filesystem Generation field in Pantheon Site Details to know whether a site has migrated. - Map your site tier to Pantheon's rollout dates so you know when to watch for behavioral changes. - After migration, smoke-test uploads, image processing, media delivery, backups and restores on storage-sensitive sites. - Review custom code for assumptions about local filesystem semantics even if Pantheon expects the migration to be transparent. - Escalate unexpected post-migration file behavior to Pantheon rather than assuming an application regression. ## What to watch - Whether Pantheon changes the rollout schedule for paid tiers. - Any migration-related incidents or compatibility notes in Pantheon status/release channels. - Additional documentation on filesystem semantics, backup behavior or performance after broader migration. ## Uncertainties - Pantheon has not published detailed benchmark data comparing Valhalla and Cloud Storage FUSE across every workload type. - The release notes do not enumerate every low-level filesystem semantic difference that custom applications might observe. ## Sources - [New filesystem used for newly created WordPress and Drupal sites](https://docs.pantheon.io/release-notes/1?category=new-feature) — Pantheon Docs · primary release notes · 2026-08-03T00:00:00+12:00. Primary source for architecture, migration schedule, no-action guidance and Filesystem Generation field.