Hi there, Suppose I have an rrd file with step=300 and good data every 5 minutes.
I want "values from the N last samples". What are the right values for --start and --end in fetch, graph or xport? If the time is now 15:08, the last good sample is from 15:00-15:05. So far so good. Now, the behaviour of rrdtool differs depending on the version we're using. In rrdtool version 1.2.11 "-start 15:00 -end 15:00" gives zero returned rows. Both "--start 15:00 --end 15:05" and "--start 15:00 --end 15:00+1" give one row with a time stamp of 1169388300 which is unixtime for 15:05. In rrdtool version 1.2.15 both "-start 15:00 -end 15:00" and "--start 15:00 --end 15:00+1" give one row with a time stamp of 1169388300 which is unixtime for 15:05, while "--start 15:00 --end 15:05" gives two rows, with time stamps 1169388300 and 1169388600: 15:05 and 15:10 (that last one being NaN since the time is only 15:08) Because of this, we've started using the "15:00+1" to get around the version dependency so that 1.2.11 and 1.2.15 behave the same. I don't see this behavioral change mentioned in the release announcements for 1.2.12 and 1.2.15 (what happened to .13 and .14?) and so I wonder if this is intentional. It "looks like" a < changed to <= or something. Also, I don't see either behaviour documented anywhere. The closest is man rrdfetch, but it doesn't mention how many and what rows to expect back given a certain resolution. I'm also assuming that a row with a timestamp of t represents the time from t-step to t. Is this "+1" solution going to work "forever" or are there more changes to come? Is there a better way to figure out --start and --end to "get the last N samples"? -- Peter Valdemar Mørch http://www.morch.com -- Unsubscribe mailto:[EMAIL PROTECTED] Help mailto:[EMAIL PROTECTED] Archive http://lists.ee.ethz.ch/rrd-users WebAdmin http://lists.ee.ethz.ch/lsg2.cgi
