RHEL6 or RHEL7 NFS client using kerberos (krb5), one user experiences slow write performance, another does not
Issue
- NFS is slow for one user on a host that has both
sec=sys
andsec=krb5
mounts. The kernel only gets into the state after some time with the user using a sec=krb5 NFS mountpoint. Once the kernel is in this state, the mount point withsec=sys
is also affected. I don't think thatsec=sys
mountpoints alone trigger this behaviour. - The definition of
NFS is slow
means NFS mounts have WRITEs capped atPAGE_SIZE
bytes/op (4KB on x86_64) even thoughwsize
is much larger - only a reboot fixes the problem. - We did not experience this issue prior to upgrading to 2.6.32-504.*el6 kernels
Environment
- Red Hat Enterprise Linux 6 (NFS client)
- kernel 2.6.32-489.el6 or above
- kernel prior to kernel-2.6.32-642.6.1.el6
- kernel prior to kernel-2.6.32-696.el6
- Red Hat Enterprise Linux 7 (NFS client)
- kernel earlier than kernel-3.10.0-514.2.2.el7
- kernel earlier than kernel-3.10.0-327.46.1.el7
- NFS mounts with mixed security flavors, some mounts have
sec=krb5
and others havesec=sys
Subscriber exclusive content
A Red Hat subscription provides unlimited access to our knowledgebase, tools, and much more.