[rrd-users] dump/fetch do not show lastupdate value

[Konstantin]

I have noticed that rrdtool dump/fetch commands sometimes populate values
as NaN even if I have written updates several times to rrd (with different
timestamps).

"lastupdate" command shows that value was successfully written, but whats
preventing it from being displayed?

Please note, that I put single values into rrd few times a day, but the
resolution is 600 seconds. So most of the values will be NaN, but why I get
NaN for periods with updated values?

here is the output:
# rrdtool lastupdate testrrd.rrd
1383560879: 800.1103515625

# rrdtool fetch testrrd.rrd AVERAGE --start 1383559800 --end 1383565200
1383560400: -nan
1383561000: -nan
1383561600: -nan
1383562200: -nan
1383562800: -nan
1383563400: -nan
1383564000: -nan
1383564600: -nan
1383565200: -nan
1383565800: -nan

# rrdtool info testrrd.rrd
filename = "testrrd.rrd"
rrd_version = "0003"
step = 600
last_update = 1383560879
header_size = 792
ds[testrrd].index = 0
ds[testrrd].type = "GAUGE"
ds[testrrd].minimal_heartbeat = 86400
ds[testrrd].min = NaN
ds[testrrd].max = NaN
ds[testrrd].last_ds = "800.1103515625"
ds[testrrd].value = 1.0164953906e+05
ds[testrrd].unknown_sec = 0
rra[0].cf = "AVERAGE"
rra[0].rows = 1095
rra[0].cur_row = 1009
rra[0].pdp_per_row = 144
rra[0].xff = 5.0000000000e-01
rra[0].cdp_prep[0].value = 4.6826486719e+04
rra[0].cdp_prep[0].unknown_datapoints = 0
rra[1].cf = "AVERAGE"
rra[1].rows = 1152
rra[1].cur_row = 1014
rra[1].pdp_per_row = 1
rra[1].xff = 5.0000000000e-01
rra[1].cdp_prep[0].value = NaN
rra[1].cdp_prep[0].unknown_datapoints = 0
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