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-rw-r--r-- | doc/administration/high_availability/nfs.md | 27 |
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diff --git a/doc/administration/high_availability/nfs.md b/doc/administration/high_availability/nfs.md index 040c9ecae55..96803746637 100644 --- a/doc/administration/high_availability/nfs.md +++ b/doc/administration/high_availability/nfs.md @@ -37,6 +37,30 @@ options: circumstances it could lead to data loss if a failure occurs before data has synced. +### Known issues + +On some customer systems, we have seen NFS clients slow precipitously due to +[excessive network traffic from numerous `TEST_STATEID` NFS +messages](https://gitlab.com/gitlab-org/gitlab-ce/issues/52017). This is +likely due to a [Linux kernel +bug](https://bugzilla.redhat.com/show_bug.cgi?id=1552203) that may be fixed in +[more recent kernels with this +commit](https://github.com/torvalds/linux/commit/95da1b3a5aded124dd1bda1e3cdb876184813140). + +Users encountering a similar issue may be advised to disable the NFS server +delegation feature, which is an optimization to reduce the number of network +round-trips needed to read or write files. To disable NFS server delegations +on an Linux NFS server, do the following: + +1. On the NFS server, run: + + ```sh + echo 0 > /proc/sys/fs/leases-enable + sysctl -w fs.leases-enable=0 + ``` + +2. Restart the NFS server process. For example, on CentOS run `service nfs restart`. + ## AWS Elastic File System GitLab strongly recommends against using AWS Elastic File System (EFS). @@ -63,10 +87,11 @@ GitLab.com: 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 ``` -Notice several options that you should consider using: +Note there are several options that you should consider using: | Setting | Description | | ------- | ----------- | +| `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. |