The Royal Pingdom blog has been measuring the downtime of five different blogging services. They are very sympathetic towards Tumblr’s position on this list, and the result will be of no surprise to anyone who uses the service. I hope they sort their problems out too.

The other standout on the list was Blogger, with no downtime over the two month testing period recorded at all!

Posterous don’t shine on this list, but I think I can happily live with a free service that goes down for one hour every month. More worrying is how users with custom domains (like mine) perform compared with subdomain blogs:

We noticed something with Posterous that we didn’t see with any of the other blogging services, and that is that for some reason the external, custom domain names that pointed to Posterous blogs were slower and occasionally timed out, which effectively resulted in more downtime. (Blogs 3 and 4 on each service use custom domain names instead of subdomains, i.e. www.example.com instead of example.posterous.com. See why under “Methodology at the bottom of this post.).

First we thought that maybe these custom domain names had DNS issues, in which case we would have removed any bad results caused by that since it wouldn’t have been fair to Posterous. However, the DNS resolution itself wasn’t slow, and what seemed to be causing the slowness was as far as we could see a series of redirects after getting to Posterous. It could be a coincidence, but Posterous might want to look into this just in case. (Posterous is welcome to contact us for more information, we’d help as much as we can.)

(via The most reliable (and unreliable) blogging services on the Web – royal.pingdom.com)