I am getting more sure this is an NFS/networking issue rather than an
issue with disks in the server.
I created a small test program that given a directory finds a random
file in a random directory three levels below, opens it and reads up to
a block (512 Bytes) of data from it and times how long it took to find
the file (opendir/readir) and read the block from the file printing the
results if the time is greater than previous ones (so seeing the peek
times). This is repeated every 10 seconds. First param is the average
time to find the file (there may not be a file 3 levels down so it
repeats those searches untill it finds one that the user can access),
the second is the time it took to find the file (3 x opendir/readdir) to
a file that existed. the last time is how long it took to open, read and
close the file.
I set one of these processes running on the server starting at the /home
dir and did the same on one of my clients that has /home NFS V4 mounted
with defaults + async.
The server after 12 hours had peak timings of (file paths hidden):
2021-10-02T09:26:38 0.008858 0.043513 0.031735 /home/...
2021-10-02T09:26:58 0.005384 0.050870 0.039186 /home/...
2021-10-02T09:38:09 0.006684 0.081707 0.014616 /home/...
2021-10-02T10:18:42 0.037394 0.144025 0.012603 /home/...
The client had timings of:
2021-10-02T08:48:45 0.056195 0.110149 0.019353 /home/...
2021-10-02T09:06:31 0.098647 0.098647 0.015171 /home/...
2021-10-02T09:28:38 1.060605 0.001996 0.000422 /home/...
2021-10-02T09:31:28 4.896196 2.037488 0.000836 /home/...
2021-10-02T11:48:44 4.423502 7.087917 1.111684 /home/...
2021-10-02T11:51:02 27.711746 45.646627 0.021321 /home/...
So at one point the NFS mounted client took 45 seconds to find a file
(opendir/readdir 3 times) and once before 7.08 seconds with 1.1 seconds
to read a block. The actual file it accessed is
46819 Bytes long and can be normally quickly accessed/copied etc.
"sar -d" reported no issues.
"mountstats /home" reported no issues
"/var/log/messages" in both systems reported no issues.
Generally the desktop system has been responsive all day (no other users
and nothing obvious going on on both server and client) and I have not
noticed a "lockup" on the GUI I have been using (intermittently). No
noticeable network errors, no noticeable hard disk read issues, but
occasional very long NFS opendir/readdir which would match up with when
i see the desktop lock up for around 30secs ore more.
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