What is CephFS?

CephFS is a file system that lives on top of a Ceph storage cluster. It lets many computers read and write files at the same time, just like a normal network drive, but it can grow to store huge amounts of data across many servers.

Let's break it down

  • Ceph: a software platform that turns a bunch of regular servers into a big, shared storage pool.
  • FS: short for “file system,” the way an operating system organizes files and directories.
  • Distributed: the data isn’t kept on one machine; it’s spread across many machines for speed and safety.
  • POSIX-compatible: it follows common standards so programs that expect a regular Unix file system can use it without changes.
  • Cluster: a group of servers that work together as one storage system.
  • Object storage: the underlying method Ceph uses to keep pieces of data, which it then assembles into files for CephFS.

Why does it matter?

Because it gives businesses a single, scalable place to store files that can handle petabytes of data, survive hardware failures, and still work with existing software. It reduces the need for expensive, proprietary storage appliances and makes it easier to grow storage as needs increase.

Where is it used?

  • Cloud service providers offering shared storage to virtual machines.
  • High-performance computing (HPC) clusters that need fast, concurrent access to large scientific datasets.
  • Media and entertainment companies storing and editing massive video files across many workstations.
  • Enterprise backup and archival systems that require reliable, long-term storage.

Good things about it

  • Scalable: add more servers and the storage capacity and performance grow automatically.
  • Fault-tolerant: data is replicated, so a single server failure doesn’t cause data loss.
  • POSIX-compatible: works with existing Linux/Unix applications without code changes.
  • Unified storage: same cluster can serve block, object, and file storage, simplifying infrastructure.
  • Open source: no licensing fees and a large community contributes improvements and support.

Not-so-good things

  • Complex to deploy and manage: requires expertise to set up the cluster, monitor health, and tune performance.
  • Higher hardware requirements: needs multiple servers, networking, and often SSDs for good performance, which can be costly upfront.
  • Performance overhead: the extra layers (object storage, metadata servers) can add latency compared to raw block devices.
  • Limited native Windows support: Windows clients need extra tools or workarounds to access CephFS.