A New World of Fault-tolerance
At VMworld 2008, VMware announced VMware FT, their solution for continuous availability (zero downtime on hardware component failures - different from HA. HA is a crash and reboot). This will stack up nicely against the likes of Marathon Technologies and Stratus who have been doing this for a while. And since everyone and their granny are rolling out a VMware based infrastructure, they will be best positioned to take advantage of it.
Stratus is currently a hardware based solution and Marathon’s is software, running on Windows Server 2003. Both of these companies have enjoyed a certain level of exclusivity but that of course will not last. I have very little info on where Stratus is going other than it can run ESX on its FT kit. Marathon have embraced the Xen hypervisor and have jumped in bed with Citrix, helping Citrix initially provide a host based XenServer HA solution (on a per VM basis!), along with their on HA solution for XenServer adding component level HA. And eventually in Q1 2009, their XenServer based FT solution will be released.
What this means, is that we will still have a choice about which hypervisor to use across all availability levels: Marathon on XenServer and VMware. This is good!
After reading a blog post from Marathon about VMware FT and some retort from a VMware supporter, I thought I’d throw in my 2p, as there appeared to be some problems with these arguments.
Firstly, the comparison is Marathon’s existing FT product that only runs on Windows against VMware’s that only runs on VMware’s hypervisor. This is a pointless comparison as they dont compare like for like and VMware’s product has not been released and wont be until some time in 2009. It would be a much fairer comparison to pitch Marathon’s new XenServer based FT against VMware’s FT…when they both arrive.
Secondly, Marathon argued against the requirement for shared storage with the VMware FT solution and the VMware guy stated that where you’d want to use FT you’ll likely have a SAN in place anyway. I have a slight issue with this. Quite often, FT solutions are used for critical production lines, health systems and emergency services. These systems may not run anywhere near a SAN, nor require one. It would be a considerable expense to require a SAN just for a 2 node FT solution. Also consider the site that has two data centres connected via fiber. We have Marathon FT systems running like this, which would allow for the likes of a site failure. This kind of setup requires that the writes are done to each system and that shared storage just doesn’t work in all cases.
Judging by the review of the FT session at VMworld by Scott Lowe, VMware may change their minds about the need for shared storage for FT. I hope so. I think it’s great that VMware is getting into this game. We have a lot of VMware sites that would be reluctant to add another virtualisation platform into the mix at this time. Being the pioneers and market leaders of server virtualisation gives them a big advantage. It widens their scope and will certainly provide decent competition for Citrix and Marathon. But, Marathon have been in the FT game for a long time too and know the problems and limitations that can be encountered in FT land. I wouldn’t underestimate them either.
Posted in: Technology Tags: Citrix, fault-tolerant, Marathon, virtualisation, VMware, Xen