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Diffstat (limited to 'doc/administration/high_availability/nfs.md')
| -rw-r--r-- | doc/administration/high_availability/nfs.md | 51 |
1 files changed, 45 insertions, 6 deletions
diff --git a/doc/administration/high_availability/nfs.md b/doc/administration/high_availability/nfs.md index 192434f7907..66f2986ab2a 100644 --- a/doc/administration/high_availability/nfs.md +++ b/doc/administration/high_availability/nfs.md @@ -148,12 +148,15 @@ For supported database architecture, please see our documentation on ## NFS Client mount options -Below is an example of an NFS mount point defined in `/etc/fstab` we use on -GitLab.com: - -```plaintext -10.1.1.1:/var/opt/gitlab/git-data /var/opt/gitlab/git-data nfs4 defaults,soft,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2 -``` +Here is an example snippet to add to `/etc/fstab`: + + ```plaintext + 10.1.0.1:/var/opt/gitlab/.ssh /var/opt/gitlab/.ssh nfs4 defaults,vers=4.1,hard,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2 + 10.1.0.1:/var/opt/gitlab/gitlab-rails/uploads /var/opt/gitlab/gitlab-rails/uploads nfs4 defaults,vers=4.1,hard,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2 + 10.1.0.1:/var/opt/gitlab/gitlab-rails/shared /var/opt/gitlab/gitlab-rails/shared nfs4 defaults,vers=4.1,hard,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2 + 10.1.0.1:/var/opt/gitlab/gitlab-ci/builds /var/opt/gitlab/gitlab-ci/builds nfs4 defaults,vers=4.1,hard,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2 + 10.1.0.1:/var/opt/gitlab/git-data /var/opt/gitlab/git-data nfs4 defaults,vers=4.1,hard,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2 + ``` Note there are several options that you should consider using: @@ -162,6 +165,42 @@ Note there are several options that you should consider using: | `vers=4.1` |NFS v4.1 should be used instead of v4.0 because there is a Linux [NFS client bug in v4.0](https://gitlab.com/gitlab-org/gitaly/issues/1339) that can cause significant problems due to stale data. | `nofail` | Don't halt boot process waiting for this mount to become available | `lookupcache=positive` | Tells the NFS client to honor `positive` cache results but invalidates any `negative` cache results. Negative cache results cause problems with Git. Specifically, a `git push` can fail to register uniformly across all NFS clients. The negative cache causes the clients to 'remember' that the files did not exist previously. +| `hard` | Instead of `soft`. [Further details](#soft-mount-option). + +### soft mount option + +We recommend that you use `hard` in your mount options, unless you have a specific +reason to use `soft`. + +On GitLab.com, we use `soft` because there were times when we had NFS servers +reboot and `soft` improved availability, but everyone's infrastructure is different. +If your NFS is provided by on-premise storage arrays with redundant controllers, +for example, you shouldn't need to worry about NFS server availability. + +The NFS man page states: + +> "soft" timeout can cause silent data corruption in certain cases + +Read the [Linux man page](https://linux.die.net/man/5/nfs) to understand the difference, +and if you do use `soft`, ensure that you've taken steps to mitigate the risks. + +If you experience behaviour that might have been caused by +writes to disk on the NFS server not occurring, such as commits going missing, +use the `hard` option, because (from the man page): + +> use the soft option only when client responsiveness is more important than data integrity + +Other vendors make similar recommendations, including +[SAP](http://wiki.scn.sap.com/wiki/x/PARnFQ) and NetApp's +[knowledge base](https://kb.netapp.com/app/answers/answer_view/a_id/1004893/~/hard-mount-vs-soft-mount-), +they highlight that if the NFS client driver caches data, `soft` means there is no certainty if +writes by GitLab are actually on disk. + +Mount points set with the option `hard` may not perform as well, and if the +NFS server goes down, `hard` will cause processes to hang when interacting with +the mount point. Use `SIGKILL` (`kill -9`) to deal with hung processes. +The `intr` option +[stopped working in the 2.6 kernel](https://access.redhat.com/solutions/157873). ## A single NFS mount |