1
1:root@GOODSERVER:/root # time showmount -e foo.bar.com > /dev/null 2>&1

real    0m0.01s
user    0m0.00s
sys 0m0.00s
1:root@GOODSERVER:/root # 

vs.: 

4:root@BADSERVER:/root # time showmount -e foo.bar.com > /dev/null 2>&1

real    1m15.04s
user    0m0.00s
sys 0m0.00s
4:root@BADSERVER:/root # 

"rpcinfo -p" looks ok on BADSERVER and GOODSERVER.

Also NFS mount is slow on the BADSERVER.

When "rpcinfo -p" finishes on the BADSERVER, it shows the output correctly.

Question: What network (?) issue could this be? AIX 7.

When I am running showmount with truss

_enrecvfrom(20, 0x200263B0, 400, 0, 0x2FF20598, 0x2FF20570, 0x00000000) = 28

It seems it doesn't gets this "enrecvfrom" - compared to the GOODSERVER.

It can resolv the domain name and we tried with only IP too.

UPDATE: DNS server is pingable and resolves domains via "dig foo.bar @DNSSERVERIP"

  • hard to guess, but it smells like name resolution timeouts; do you have an unreachable DNS server in the mix? – Jeff Schaller Jan 29 '17 at 15:20
  • even if we use only IP? is NFS that bad? :) – pepite Jan 30 '17 at 6:04
  • There could be many reasons, depending on your network. Incorrect defined routes, incorrect configured spanning tree atm. If possible try some network monitoring (wireshark, tcpdump, ...) when issuing showmount to see what's going on (packages lost, different routes, ..) – ridgy Feb 5 '17 at 12:25
  • 1
    Test the DNS Reverse Lookup on host foo.bar.com, host 10.9.8.7 should show the FQDN of your bad host. And host badhost.example.com must solve to the right IP address again. (replace 10.9.8.7 and badhost.example.com with your corresponding data) – ingopingo Feb 5 '17 at 13:06
  • 1
    As @ingopingo states, it's likely the server at foo.bar.com that's having problems doing reverse DNS lookups of the IP address of the request from your badly-performing server. foo.bar.com could be configured to log requests by FQDN, for example, and your badly-performing server can't be found by reverse DNS lookup of its IP. In other words, the problem is on foo.bar.com. – Andrew Henle Feb 5 '17 at 13:29

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