45 second event happened at: 2021-10-02T11:51:02 UTC. Not sure
what sar time is based on (maybe local time BST rather than UTC
so would be 2021-10-02T12:51:02 BST.
Continuing info ...
sar -n NFSD on the server
11:00:01 24.16 0.00
24.16 0.00 24.16 0.00 0.00 0.35
1.48 2.07 21.08
11:10:01 21.13 0.00 21.13 0.00 21.13
0.00 0.00 0.28 0.89 1.72 19.58
11:20:02 17.85 0.00 17.85 0.00 17.85
0.00 0.00 0.27 0.69 0.82 16.65
11:30:02 20.66 0.00 20.66 0.00 20.66
0.00 0.00 0.29 0.83 1.42 19.15
11:40:02 39.80 0.00 39.80 0.00 39.80
0.00 0.00 0.89 2.05 3.67 25.51
11:50:02 35.40 0.00 35.40 0.00 35.40
0.00 0.00 0.39 0.65 1.22 18.21
12:00:02 41.85 0.00 41.85 0.00 41.85
0.00 0.00 0.84 1.14 2.08 20.50
12:10:02 38.54 0.00 38.54 0.00 38.54
0.00 0.00 0.48 0.82 1.48 19.62
12:20:02 39.85 0.00 39.85 0.00 39.85
0.00 0.00 0.37 1.50 1.29 19.44
12:30:02 39.84 0.00 39.84 0.00 39.84
0.00 0.00 0.70 1.03 2.28 19.78
12:40:02 38.29 0.00 38.29 0.00 38.29
0.00 0.00 0.46 0.81 1.26 19.37
12:50:02 71.38 0.00 71.38 0.00 71.37
0.00 0.00 1.12 2.41 8.19 34.87
13:00:00 77.46 0.00 77.46 0.00 77.45
0.00 0.00 1.43 3.30 7.36 38.31
13:10:00 67.62 0.00 67.63 0.00 67.62
0.00 0.00 3.85 2.84 4.68 29.66
sar -n SOCK on the server
11:20:02
480
41 32 1 0
0
11:30:02 482
41 32 1 0
4
11:40:02 480
41 32 1 0
0
11:50:02 480
41 32 1 0
1
12:00:02 480
41 32 1 0
1
12:10:02 480
41 32 1 0
1
12:20:02 480
41 32 1 0
1
12:30:02 480
41 32 1 0
1
12:40:02 480
41 32 1 0
1
12:40:02 totsck tcpsck udpsck rawsck ip-frag
tcp-tw
12:50:02 480
41 32 1 0
1
13:00:00 480
41 32 1 0
1
13:10:00 490
43 32 1 0
1
sar -n NFS on the client
11:10:02
19.82 0.00
0.28 0.34 0.71 15.13
11:20:03 16.53 0.00
0.27 0.15 0.34 13.80
11:30:04 17.20 0.00
0.13 0.08 0.30 15.17
11:40:04 37.46 0.00
0.89 1.47 2.07 14.42
11:50:05 32.97 0.00
0.28 0.11 0.34 15.00
12:00:05 36.31 0.00
0.59 0.47 0.75 14.17
12:10:06 34.77 0.00
0.36 0.26 0.65 14.95
12:20:07 37.55 0.00
0.27 0.97 0.35 15.36
12:30:07 33.90 0.00
0.46 0.37 0.62 13.47
12:40:07 35.67 0.00
0.36 0.28 0.64 15.44
12:50:07 68.97 0.00
1.01 1.89 6.64 13.28
13:00:07 71.08 0.00
1.17 2.58 4.32 17.87
13:10:07 49.28 0.00
0.84 1.55 1.81 15.23
13:20:00 41.87 0.00
0.50 1.24 0.87 14.98
sar -n SOCK client
11:20:03
1166
39 14 0
0 0
11:30:04 1164
35 14 0
0
2
11:40:04 1191
50 15 0
0
1
11:50:05 1182
40 14 0
0 0
12:00:05 1182
39 14 0
0
2
12:10:06 1182
39 14 0
0
3
12:20:07 1171
39 14 0
0
1
12:30:07 1179
40 15 0
0 0
12:40:07 1179
39 15 0
0 0
12:50:07 1200
45 17 0
0
1
13:00:07 1188
40 14 0
0
2
Nothing
obvious I can see there ...
Terry