Building highly available shares, DFS namespaces and replication topology (DFS-R) – Part 4 – What is replication? How DFS-R works? Can I use it as backup?

Backup

  • All types of replication (file replication – DFS-R, Hyper-V Replica, Volume replication – vNext) are not a backup. The reason is that if you do a mistake then the mistake is replicated to all servers.
  • Replication is great for disaster recovery (DR) when for example a plane crash on your datacenter.
  • Replication is also great for example in order to do a decommission one site and replace it by another site (DFS-R and Hyper-V Replica can be used) because if the process is done correctly then the service remain online.
  • Backup is something different. Backup mens that you can go back in time and backup is also a protection when a user or administrator do a mistake.
  • Resolution: Always do backups.

DFS-R disadvantages

  • Replication is not synchronous.
    • When a File Server (or clustered File Server) on the client”s site is down then the client is directed to another File Server in the site (if there is one) or to another site. That makes the share highly-available but data on different server could be outdated.
  • It is not possible to replicate locked files.
  • It is not a good idea to replicate application data.
    • Using DFS-R it is not possible to create consistent snapshots (like VSS do) and therefore some files can be current and some files could be older.
    • Do not use DFS-R for application data even when application do not lock files.
  • No native monitoring.
    • To monitor state of the replication and health of the servers and replication topology it is required to use custom scripts or management pack (MP) for System Center Operations Manager (SCOM).
  • Resolution: DFS Replication is suitable for classic File Servers but administrators have to understand the disadvantages and make decision if it is not a problem for their scenario.

DFS-R as the way how to transport data to a server that do a backup

  • This is possible and this is also a common practice.
  • It is possible to have one main site (Hub) and multiple sites (Spoke) and Hub and Spoke topology.
  • But the disadvantages of the DFS-R remain and that mean that this setup can be used only when those disadvantages are not an issue.

One Comment on “Building highly available shares, DFS namespaces and replication topology (DFS-R) – Part 4 – What is replication? How DFS-R works? Can I use it as backup?

  1. Hi Rudolf, Thank you for this post. But i want to ask: Why you think that It is not a good idea to replicate application data? Can you explain it further? When files generated by some application (maybe as result of processing) are not locked by that application -why the replication with DFS-R to other place schould be a problem? Or is there another meaning? Thank You again.

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