Which hosting service is the most reliable in terms of uptime? Do you personally use that service and if not, what factors led you to choose a different service?

Best is a relative term. Do you consider 1000 days without a reboot "best", or a host with less than 30 days consecutive uptime? Keep in mind that if you have 1000 days on a realworld production server and never run a reboot or had a moment of downtime then the server hasn't had any recent kernel updates or software updates (leaving the server open to hackers etc).

I do have a testing server here that has exceeded 600 days uptime currently, but it's not a production machine and used only internally in our company.

So "best" is a relative term. What do you consider best?

What sort of budget do you have? Any specific requirements? Perhaps we can recommend a few reliable providers to you that have a proven track-record of uptime

The host should be able to inform you about the Server Maintenance schedule. If the host is capable of providing you the best uptime with the weekly maintenance and should be able to provide complete assistance without any additional charges. I have seen hosts charging around 5-10 USD for simply changing the primary domain name for the hosting account.

Thanks for the information. I'm a complete newbie so I didn't consider downtime for maintenance at all. Downtime is inconvenient but I imagine it'd be short in duration and improve security.

As a non-server admin, I wonder how stuff like Ksplice is changing the standards regarding that.

To expand on your point though, just because the machine is up and running, it doesn't mean that it was working properly, serving pages all the time. Sadly, few hosts have the... courage to post public uptime records, so one has no way to really compare this aspect of the hosting service.

There are a number of uptime sites where you can catch a glimpse of a providers performance. None of them tell the whole story though - mostly uptime on one or two servers. Like Conor said, maintenance is necessary and your provider should notify you well in advance of any downtime windows.

This question is impossible to answer. You can always check the monitoring stats that Netcraft publishes on their website. However Netcraft does not monitor all web hosting providers.

I'm a big fan of ksplice - and it's been great, but I still do monthly reboots on servers in order to flush anything out of memory that may be hanging around and keep the system running optimal.

The problem I have with uptime reports is that they're hard to guage. We have 400 servers, and while we may have 300 with 100% uptime over the past 5 days, if a user rebooted their server for any reason (dedicated server), or their site was hacked - that really shouldn't fall under OUR uptime performance as it was the fault of the user, not us.

Outside monitoring services monitor a domain or IP number for either a HTTP response or Ping response (depending on service). If their apache crashes for any reason, that's a negative mark. If they didn't pay their bill and their server is disconnected, that again is the fault of the user, and not us as a hosting company.

It's very hard to show public information as to uptime as a simple reboot may be necessary to upgrade a kernel or PHP and that then shows 99.98% uptime, even though it was scheduled maintenance.

We're asked all the time how long our servers have been up, but with so many, you can't just say 100% or 99.9% as there's many caveats as to why something may have been offline.

Even here on hosting discussion. For the most part, the server has been online and working over the past 2 years - but there have been 2 and 5 minute outages each month in order to upgrade scripts and keep things operating correctly. Is the site considered online 100% - technically, no.

Self managed (or root enabled) dedicated servers would definitely not be a fair inclusion in the uptime reports of a hosting company.

I agree with some guy said above,Best is a relative term.
There is no absolute best. The best uptime personally is more than the smooth server runtime, the quality technical support also is a significant factor .

Always use third party reporting service.

One thing you can do is see if you can get a few sites hosted at a provider and put some uptime checks on them (such as a free pingdom account for 30 days) or see if the provider has uptime reports that they can show you...

Third party reports are obviously going to be the best as they're not able to be doctored, or at least, not as easily.

You can use services like siteuptime.com for monitoring your site uptime......

I would not be bothered with needed reboots and downtime, but when it comes to regular outages, crashes and problems, then I would not be happy.

We understand things have to be done, we do it on all of our servers, but providing I am told a day before, it is fine.