[OmniOS-discuss] Slow NFS speeds at rsize > 128k

[Stephan Budach]

Hello everyone,

I am sharing my zfs via NFS to a couple of OVM nodes. I noticed really 
bad NFS read performance, when rsize goes beyond 128k, whereas the 
performance is just fine at 32k. The issue is, that the ovs-agent, which 
is performing the actual mount, doesn't accept or pass any NFS mount 
options to the NFS server. To give some numbers, a rsize of 1mb results 
in a read throughput of approx. 2Mb/s, whereas a rsize of 32k gives me 
110Mb/s. Mounting a NFS export from a OEL 6u4 box has no issues with 
this, as the read speeds from this export are 108+MB/s regardles of the 
rsize of the NFS mount.

The OmniOS box is currently connected to a 10GbE port at our core 6509, 
but the NFS client is connected through a 1GbE port only. MTU is at 1500 
and can currently not be upped.
Anyone having a tip, why a rsize of 64k+ will result in such a 
performance drop?

Thanks,
budy

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