Date: Sat, 9 Nov 2002 17:04:58 +0100 (MET) From: Michael Grant <mg-fbsd3@grant.org> To: freebsd-cluster@FreeBSD.ORG Subject: clustering freebsd Message-ID: <200211091604.gA9G4wW28126@splat.grant.org>
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I'm new to the list (but not new to unix!) I've been running freebsd for years now on a box I colo. I've got some clients and sell some services on my box. I'm becomming very interested in creating a smallish cluster of machines to make my little operation more reliable. One of the big things that cause me down time is upgrading the OS. I'm also worried about hardware failure (which luckily hasn't happened to me yet...) I too would like to achieve at least 5 nines. I read all the archives of this list back to january 2002. Andy's phase-2 project definitely sounds cool. Let's say I have a cluster of n machines. Some of those n machines may be running a web server, some a shell server, some mail server, some pop/imap mail servers...etc. How is an incoming connection sent to the right machine? It seems like that there needs to be a single machine in front of the cluster to send connections the right way, isn't this a single point of failure? If you do have multiple machines answering requests, how's this done? With multiple IP addresses? I know one can specify multiple A records in DNS and that it'll do a sort of round-robin. But does this work well? What if one of the machines is down and a caching dns server returns an ip address of one of the down machines? Seems like you need then to start modifying the dns zone to take out the down machines and use a low ttl. This starts to get ugly quickly. Second problem I have been thinking about is shared disk. I read a post by someone who also had this concern. One obvious way to solve the shared disk problem is to have another box which has a bunch of disks in a RAID configuration, and mount the diks via nfs. This disk box would probably need to be highly available with redundant power supplies and the like. However, I'm not so convinced that a third disk box is the right answer. I'd like to see something which could mirror (in real time) a file system over the lan, thus keeping 2+ disks in sync just like a RAID array spread over multiple systems. Does such a thing exist? After hours of searching, I could find nothing that did this. There seems to be essentially 2 types of clustering: 1) hot spare failovers 2) multiple machines operating in parallel (Perhaps someone could enlighten me if there are proper names for these). It would seem that Andy's phase 2 is more like #2 and his phase 1 is more like #1 above. I'm definltey more insterested in #2. I'm very interested to find something which lets me run n machines to provide a a bunch of services. I don't mind if they all look like one machine or several at this point, I'm not sure if that's important to me. What's important to me at the moment is that if I have a user on one machine that goes down that they can get right back on another machine and get at their mail or files. Of if someone is surfing our site, they just automatically get files from the server that's up. So, after thinking about dns headaches and single machines in front of a cluster, I'm totally exasperated to figure out what the right thing to do is. Does anyone know of some list of clustering software? Is there anything I can use today to do #2 that runs on freebsd (or other bsd systems)? Sorry for such a long rant, but I hope that this sparks some chitchat on this otherwise seemingly dead list. Michael Grant To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-cluster" in the body of the message
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