We are hosting 32 websites in one Standard web hosting plan mode and a Small instance size. Will it cost us more to enable "Always On" in one or all of the websites?
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Azure unloads your site if it is idle for the standard 20 minute timeout, which can cause slow responses for the initial site users after it is unloaded. Enabling Always On essentially causes Azure to automatically ping your site periodically to ensure that it remains in a running state. There is no charge for enabling Always On, but is not an available option on lower end plans. I suppose in theory it could consume more CPU cycles and thus could require the deployment of more infrastructure if you have many, many sites.
As an aside, "Always On" for Azure websites should not be confused with AlwaysOn Failover Clustering/Availability Groups for SQL Server.
phoebus
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FYI, "always On" doesn't ping the apps to keep them up it simply shuts off the mechanism that turns off the idle app. – MikeWo Aug 15 '14 at 19:32
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@MikeWo That's not what this blog post from Scott Guthrie at Microsoft indicates: http://weblogs.asp.net/scottgu/windows-azure-staging-publishing-support-for-web-sites-monitoring-improvements-hyper-v-recovery-manager-ga-and-pci-compliance - "When Always On is enabled on a site, Windows Azure will automatically ping your Web Site regularly to ensure that the Web Site is always active and in a warm/running state." – phoebus Aug 15 '14 at 19:33
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3While this is interesting information, it doesn't clearly answer the question. What do you mean by, "it does not cost you more, beyond the fact that it might theoretically consume more CPU cycles." It seems like that would make it cost more. Does it? – Shaun Luttin Aug 15 '14 at 19:34
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2@ShaunLuttin If you consume more cycles you could theoretically require deployment of more resources, which costs money. AlwaysOn in and of itself doesn't cost money. It's a pedantic aside at best I admit but commentors on SF sometimes force one into pedantry :) – phoebus Aug 15 '14 at 19:36
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Is this similar to asking, "Would more website traffic cost more money?" While more website traffic doesn't cost more money per se, it will consume more CPU cycle, and therefor cost more indirectly. Is it a similar situation with Always On? – Shaun Luttin Aug 15 '14 at 19:47
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@ShaunLuttin Theoretically yes, but with 32 sites it's minuscule. Even if they loaded the complete front page of each site once every five minutes that's still only 384 additional hits per hour total across all sites, and my guess is they don't even do that, it's probably more of an internal thing. – phoebus Aug 15 '14 at 19:49
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@phoebus Apologies, I was partially incorrect in my statement, in that it does do the pinging as you say, but it also shuts off the feature that takes it down on Idle. I get that from comments in http://stackoverflow.com/questions/25326245/can-a-standard-or-basic-azure-website-instance-be-pulled-down-by-the-arr-ma where Zain Rizvi indicates as such. He is a dev on the Web Sites team. – MikeWo Aug 15 '14 at 21:13
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When i enabled "Always-on' I get a web request every 2 minutes. All it does it simply make a http request to your root every 2 minutes. – Zapnologica Apr 18 '16 at 08:43