NFS write performances issue
I have a huge NFS v3 write performance issue on a web server. All servers are virtual machines
It's a RHEL 5.6 x64 server with a NFS mount from a RHEL 5.8 x64 with multipath. Physical drives are hosted on an IBM high perf storage (IBM N6240 E21 : disk FC 15 k).
Write speed are as low a 250KB/sec. Here are the tests done :
- Write to NFS mount : 250KB/s
- Write to /root from sftp (FileZilla) : 10M/s
- Write to NFS mount from sftp (FileZilla) : 250KB/s
I mounted the same disk to another server and speeds are ok.
Mounting another disk, speeds are slow.
NIC seems ok since transfers from client to the webserver /root is fast enough.
When using async transfers are fast but when it reachs 100% nothing happens until the file is written and the io% are up to 95-99%.
Here are my mount options
I don't know what to look for now.
Edit : the web server was in another VLAN with a firewall between him and the NFS server. Moved the web server to the same VLAN, no changes, switched to NFS v4, no changes.
I suggest trying different/no mount options on the NFS server.
Try mounting from a non RHEL system.
Just took off the sync option on the client side and everything is back as it should be. Don't know why this option f*ck everyhting up.
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