High I/O wait to NFS share on NAS
Issue
- Our RHEL server runs processes to generate files. The files are stored on a NAS accessed over NFS.
- Our server serves these files to a client via
vsftpd. The speed of the FTP jobs has dropped from 60~70Mbps to ~160kbps. - We have observed high IO wait and FTP processes in D state for some time.
- Remounting the NFS share results in all clients dropping out and failing, but high speed returns for a short time time.
Environment
- Red Hat Enterprise Linux 5
- RHEL system is NFS client to a NAS filer
- RHEL system is FTP server to external FTP clients
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