Grid hosting providers may offer advantages over dedicated servers, but they’re not immune to downtime. Mosso, a utility computing start-up launched earlier this year with backing from Rackspace, has experienced a significant outage today. The mosso.com web site was offline for more than an hour this morning after a series of shorter outages yesterday.

Mosso uses a “hosting system” of clusters of servers, an approach initially seen in enterprise hosting, which can offer advantages in redundancy and performance. The company is one of a growing number of hosting providers moving to grid hosting as an alternative to discount dedicated servers, which have been enormously popular with hosting resellers and power users. Improved reliability is among the key selling points for grid systems.

A dynamically updating chart of the performance of the Mosso.com is available. Netcraft offers a web site performance monitoring service that provides detailed uptime charts, along with e-mail alerts when an outage occurs.