# [rrd-users] Graph strange lag on datas

Tntteam tntteam at free.fr
Mon Mar 7 16:55:39 CET 2011

```Hi,

I have a strange behavior on my graphs.

Here is the data source I use to generate the graph :

http://img11.imageshack.us/i/image001ki.png/

As you see I inserted manually a 10 value to generate a high point in the graph.

The timestamp 1299062660 is 11:44:20 (GMT +1)

Now is the output rrd graph :

http://img534.imageshack.us/i/image002pjf.jpg/

And my rrd definition :

rrdtool info 1.rrd :
filename = "1.rrd"
rrd_version = "0003"
step = 60
last_update = 1299063080
ds[time].type = "GAUGE"
ds[time].minimal_heartbeat = 600
ds[time].min = NaN
ds[time].max = NaN
ds[time].last_ds = "1.800000e-02"
ds[time].value = 3.6000000000e-01
ds[time].unknown_sec = 0
rra[0].cf = "AVERAGE"
rra[0].rows = 525600
rra[0].cur_row = 304990
rra[0].pdp_per_row = 1
rra[0].xff = 5.0000000000e-01
rra[0].cdp_prep[0].value = NaN
rra[0].cdp_prep[0].unknown_datapoints = 0

As you can see, only 1 point is needed to make a CDP.

Something I don’’t understand is why the high point in my graph starts
at 11h43, then go down a little at 11h44, and drops at 11h45, when the
high data point is at 11h44.

Because the value at 11h43 is 0.021 as you can see in my mysql data points …

Why is there such a lag of 1 interval ?

I hope you understood me :=)

Thanks for any help

```