Hello,

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

rw,user,rsize=4096,wsize=4096,nosuid,intr,tcp,noatime,nodev,sync


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.

HO SH*T.

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.