Forum Moderators: phranque
just want to locate a specific 2 hour time location and verify no traffic ..but cant seem to find out how or even if I can with the available tools
if it saved these (older dates) which file would it be in?
It works fine, continually monitors your site and sends instant alerts when it goes down, then sends you a recovery alert with the exact amount of time it has been down.
you can monitor 2 sites for free..
I think I like the speed of it and I can tell my server to the second on which day at which time it was down with out checking logs etc ..
In order to give you an exact server downtime -- to the second -- they would have to send a request to your server twice per second, and not many Webmasters would desire that frequency of access. It would also cost the service provider more in terms of bandwidth, and make it harder for them to provide the service free or at low cost.
In simplifed terms, here's how it effectively works for a given server:
Jim
In order to sample something and report a state change to an accuracy of time interval I, you must poll at an interval of I/2. That assumes that the polling frequency for both states of a 2-state system is the same. In this case, it is not; They poll slowly for failure, and poll much faster for recovery. The best accuracy thay can achieve if they poll once an hour for failure and infinitely fast for recovery is a one-hour accuracy.
To illustrate: They could poll once an hour, and polling it just before your server died, find it OK. They would not poll again for one hour while your server is still down, and then poll again after this first hour. At this time (after the first hour), they would find it down, and then begin polling very fast - say once per second. If, after the first hour and one second of actual downtime, the server came up, they would see that it had been down only for one second.
Actually, they used to poll once an hour, give or take a (very) few minutes. In the past several years, though, I've seen them polling less frequently, and with a much larger variation in the sampling rate. I guess they just have too many subscribers, and too few machines to run their polling client on.
Regardless of the advertising hype and the description on their site, they cannot achieve the accuracy they imply in the downtime report with such a slow failure sampling rate. No-one can break the laws of physics -- or Nyquist and Shannon. This is not to say the service is not useful -- it is. But you need to understand what you're getting.
Their paid service undoubtedly polls faster, and thus will have better downtime report accuracy.
Jim
Lobo, the accuracy depends entirely on the polling frequency. If they poll your sites faster, then the report will be more accurate. But even on my sites, where they poll (about) once an hour, the downtime report still shows hours:minutes
I don't think they mean to mislead, but it's just impossible to get that accuracy with the one-hour polling rate on my sites.
Jim
