Dear Falko
The max values for rsize and wsize is 8096 (8K) and this is a default already when OPTIONS is not specified.
1) Have you check if any other client(s) to this NFS server (say, from Windows/Linux PCs) does not experience the same performance issue accessing the same target NFS server file(s)? If IBM i is the only NFS client to have the performance issue, check a few factors in IBM i memory pool number 2 (*BASE) with WRKSYSSTS command as IBM i NFS client job runs in this memory pool by default.
2) First check the parameter MAX ACT of pool 2. It should have a value of 1,000 or higher. This is because, by default, pool 2 runs very many threads of many IBM i OS jobs which includes IBM i NFS server and client by default, If the MAX ACT value of pool 2 is much less than 1,000, it can be a possible cause of your problem and you should change it to at least 1,000. Increasing MAX ACT of a memory pool generally can be done on-line with no disruption to the entire system. (Decreasing should be done at low workload period.)
3) If action 2 does not solve the issue, then check if memory pool 2 has high faulting rate or not while you use NFS client? High fault rate is a value in the range of 1,000 or more (assuming IBM i server uses HDDs, as opposed to SSDs). Press F10 to see instantaneous value (NOT F5 which shows average value over elapsed time). If it is high, you need to increase the size of pool 2 to reduce the faulting rate down.
If you still have the problem after taking all the above actions, you need to explain what you did in some details that leads you to the performance issue.
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Satid S
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Original Message:
Sent: Wed December 17, 2025 10:23 AM
From: Falko Huetter
Subject: IBMi Performance Problems with NFS (Client)
Hi together,
I'm experiencing performance issues with the NFS client on IBM i with V7R4 TR11.
I want to use the following options in the mount command:
===> ADDMFS TYPE(*NFS) MFS('nfs-server:/') MNTOVRDIR('/nfs') OPTIONS('rsize=524288,wsize=524288')
I'm getting CPFA1BB back with the option keyword "rsize not within the range".
1. However, these options are not being accepted. What would be the correct values for rsize/wsize?
2. Can I force the client to use TCP instead of UDP?
3. Does anyone have a better idea how I can optimize NFS on my IBM i?
Thanks in advanced
Falko
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Falko Huetter
Consultant
PROFI Engineering Systems AG
Darmstadt
0049 6151 82900
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