[rrd-users] RRD PERCENT question (95 percentile)
Andree Toonk
andree.toonk at bc.net
Wed May 12 20:31:17 CEST 2010
Hi Alex, List,
.-- My secret spy satellite informs me that at 12/05/10 12:08 AM Alex
van den Bogaerdt wrote:
> Please see if the number on position 1095 or 1097 equals that of what
> rrdtool finds.
It seems that the numbers most closely are on position:
1089 for IN
1086 for OUT
So that's strange for 2 reasons. One I can't seem to find the exact
sample value in the output of RRD fetch. Even is it uses round, it's
still quite far of.
Two, the values are on different positions (in / out).
> Your calculation: 1153 samples, 95% = 1095,35 so you take 1096.
> RRDtool: round(95*1152/100)=1094, based on an array with first member is 0,
> so 1094 is the 1095th position.
> If I recall correctly, the original version did use truncation instead of
> rounding, which makes no difference in this case.
>
> Anyway, unless I made a mistake here, rrdtool takes data[1094] and you take
> data[1096]. Your returned value should be higher than what RRDtool reports.
This is what RRDtool reports:
95IN 8.6721M
95OUT 8.4774M
These are some the sorted 'fetched' values:
IN/OUT position Value Timestamp
IN 1080 8129584 1272047400
IN 1081 8193496 1272054900
IN 1082 8297464 1272160800
IN 1083 8412152 1272054300
IN 1084 8547928 1271906400
IN 1085 8551208 1272052200
IN 1086 8647712 1272060000
IN 1087 8686832 1272055500
IN 1088 8688120 1272159600
IN 1089 8828728 1272057600
IN 1090 8846536 1272050400
IN 1091 8966696 1272052500
IN 1092 9055064 1272238800
IN 1093 9121816 1271895600
IN 1094 9123760 1272050700
IN 1095 9164488 1272159000
IN 1096 9227448 1272234600
IN 1097 9234184 1272057000
IN 1098 9264672 1272049200
IN 1099 9275656 1272058200
IN 1100 9283128 1272237000
OUT 1085 8228392 1272040200
OUT 1086 8370536 1272050400
OUT 1087 8382904 1271894400
OUT 1088 8423032 1272049500
OUT 1089 8478456 1272061500
OUT 1090 8482616 1272058200
OUT 1091 8489504 1271904300
OUT 1092 8518072 1271973900
OUT 1093 8725088 1271961900
OUT 1094 8759296 1272062400
OUT 1095 8843688 1271998500
OUT 1096 8851120 1271953500
OUT 1097 8864888 1271997600
OUT 1098 8878360 1271966400
OUT 1099 9039032 1271964600
OUT 1100 9050112 1271997300
>> I would like to use RRDtool for this, but need to be sure that the
>> numbers are correct, i.e understand why the numbers are different than
>> when calculated manually.
>
> I would also worry why it is opposite to what I reasoned above.
Yes indeed.
Based on the above I'm still worried. I can only imagine I am doing
something wrong when verifying or it's something in RRDtool.
As I mentioned I've posted all data + scripts here:
http://toonk.nl/rrdtest/
I would really appreciate if someone could verify this as well. Based on
what I've tested so far it seems to return a 'incorrect' result. Or my
test script is doing something wrong.
Any help is greatly appreciated.
Thanks,
Andree
--
Andree Toonk
BCNET
Suite 7300, SFU Harbour Centre
515 West Hastings St.
Vancouver, BC, V6B 5K3
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