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I have a couple of ubuntu servers on a virtual environment (Ubuntu 16.04 + 22.04 on vmware). There is a NFS Mount to a NFS Share which is in a different Network. Now if i execute any command to this NFS Share (find /var/tmp/test001 -type f) or "(tar -czf /var/tmp/test001/test001.tar /var/tmp/test001/subdirectory) the time it takes to execute the command varries for the same command.

For example, first time it is fast. Then it is slow. Then it is faster again.

It seems to be related to the number of rpc calls made which i can observe with "nfsstats -Z" while executing the command.

Example:

1 minute for 50'000 rpc calls

2 minute for 100'000 rpc calls

30 second for 25'000 rpc calls

This is the NFS4 mount:

1.2.3.4:/path_to/remote_nfs001 on /var/tmp/test001 type nfs4 (rw,relatime,vers=4.0,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=2.3.4.5,local_lock=none,addr=1.2.3.4)

NFS Client Version:

/sbin/mount.nfs4 -V
mount.nfs4: (linux nfs-utils 2.6.1)

Do you know why there is a difference in the number of prc calls made for the same command? I also observed if it's related to the type of call (getattr, readdir, open, close) But this does not indicate any influence. The relation for time is the number of calls. The same observation is also made if i use tcpdump to check the packets. There you also see the different number of calls each time.

On the NFS share there are a lot of folders and around 15'000 Files

RPC Call for 19 seconds execution

RPC Call for 9 seconds execution

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  • With RPC Debug Log i found out now that on the "slow" case it executes the revalidation two times. It does all decode_attr* commands two times until it reaches nfs_lookup_revalidate_done. Can you explain why?
    – nussi
    Commented Jan 9 at 15:18

1 Answer 1

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The issue was not in the RPC protocoll or NFS share. It was bad wiring in the Datacenter. Only a few ESXi Hosts were affected. They had 3x the amount of latency. The 2x amount of latency is explainable trough the geolocation of one of the DC

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