Write throughput to RHEL NFS server drops to 1-2 MB/s due to due improper network tuning
Issue
- Writing to an NFS filesystem is extremely slow. Kernel reports hung_task_timeout_sec. Write speeds are anywhere between 1.7MB/s and 2.4MB/s while speeds should be at least 20times as fast. This is tested using dd if=/dev/zero of=toto count=10K bs=1K
- On RHEL 7.1 NFS client, which mounts NFS share from RHEL 7.1 nfs server. Writing to the same NFS server and to the exact same NFS share from another RHEL 7.1 NFS client at the exact same time is fast. On our RHEL 7.1 NFS client systems, memory gets hot-added/increased from 4GB up to 64GB depending on the application that needs to run on the system. Could this have any impact? We were using the same design NFS client, NFS server, hot adding memory on RHEL 5.5 and there we never experienced these issues.
- Write throughput on NFS server drops to 1-2 MB/s due to due improper network tuning
- Rebooting the NFS client system makes things go fast again
- Unmounting & remounting the NFS share makes writing fast again
Environment
- Red Hat Enterprise Linux (RHEL) 7
- Red Hat Enterprise Linux (RHEL) 6
- NFS server
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