What should I use for shared storage across multiple app servers?

It depends on what your app servers need from shared storage, but the most common choices are:

Best default choices

• Object storage like Amazon S3 / Google Cloud Storage / Azure Blob

  • Best for: uploads, assets, backups, logs, static files
  • Pros: highly durable, cheap, scalable
  • Cons: not a traditional filesystem; slower than local disk; app changes needed sometimes

• Managed network file storage like AWS EFS / Azure Files / Google Filestore

  • Best for: when multiple servers need the same POSIX-like filesystem
  • Pros: mounted like a shared directory, easy for existing apps
  • Cons: can be slower and more expensive than local disk; not ideal for heavy low-latency workloads

Other options

• Distributed file systems like CephFS, GlusterFS, Lustre

  • Best for: on-prem or specialized environments
  • Pros: scalable, flexible
  • Cons: more operational complexity

• Shared block storage

  • Usually not the right answer for multiple app servers, because block devices are generally meant to be attached to one server at a time unless you add clustering/locking layers.

Rule of thumb

• If you need files shared across app servers: use managed NFS/file storage
• If you need uploads/static content/backups: use object storage
• If you need very high performance or special on-prem requirements: consider CephFS or a similar distributed filesystem

Important design note

For web apps, the best practice is often:

• keep app servers stateless
• store user-generated files in object storage
• store session/state in a database or cache like Redis

If you tell me your stack and workload (e.g. web app, media uploads, VM images, on-prem vs cloud, Linux/Windows), I can recommend the best specific option.