Date: Wed, 25 Jul 2001 11:47:35 +0200 From: Gabriel Ambuehl <gabriel_ambuehl@buz.ch> To: Paul Robinson <paul@akita.co.uk> Cc: Enriko Groen <enriko.groen@netivity.nl>, 'Tony Saign' <tony@saignon.net>, freebsd-isp@freebsd.org Subject: Re[2]: Redundant setup on a budget?? Message-ID: <1241681557.20010725114735@buz.ch> In-Reply-To: <20010724154211.C34017@jake.akitanet.co.uk> References: <510EAC2065C0D311929200A0247252622F7A7B@NETIVITY-FS> <20010724154211.C34017@jake.akitanet.co.uk>
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-----BEGIN PGP SIGNED MESSAGE----- Hello Paul, Tuesday, July 24, 2001, 4:42:11 PM, you wrote: > The way I see it, I'm loathed to spend £20k+ for a decent L4 load > balancing Not as much maybe. www.coyotepoint.com could help you out for about 5000$ (which is based on FreeBSD, BTW!). > and look at writing it. Polyserve offer a commercial solution and I > believe that a copy of their software is shipped with an eval > license if you buy FBSD CDs from Walnut Creek, but I've never > played with it. I have however seen it demo'ed at a trade show in > London, and to me it looked more suited for the primary/backup > configuration, that I also don't wish to use. ACK. Conventional fail over for clustering. > I have a huge workload on at the moment, but on the bottom of the > pile is to dedicate some time to playing with clustering stuff like > web, mail and mysql servers under FBSD, documenting up the > experience, and putting it up somewhere public. Until that point, > do any of you guys have any resources, or even better, whitepapers > or (gasp!) software for FreeBSD clustering? Actually, there is, sort of at least. Look into the ipfilter package (shipped with FreeBSD 4.3 or on http://coombs.anu.edu.au/ipfilter/) and especially its l4check tool. If that is not enough, we're currently implementing a monitoring system with many of the functionality found in netsaint (which unfortunately is crashing all the time on our machines and also a bit slow, OTOH, I can't yet say whether ours will be much faster) and NAT modifying features[1]. It isn't yet decided under what kind of license this thing will get released, but if someone's willing to play alpha tester, I could provide you surely with a free license so you could play with it. I also have an alpha version of a whitepaper on my disk but that one's in German (high class one, riddled with English fail over vocabulary), so I suspect it wouldn't help you very much. Basically, the load balancing part is easy enough (look ipfilter and natd, both do it). Harder but still doable with a reasonable amount of work is fail over (l4check might be good enough for your uses, for us it was too limited). What's really hard is to mirror the servers in near realtime (and here are WE searching for a solution). While databases bring their own replication features, filesystems do not (with the possible exception of coda but that beast did neither work on my systems nor does it look like it's being maintained). The Linux crowd got several solutions to achieve realtime mirroring on filesystem layer, most notably distributed RAID through the use of one network block device (which FreeBSD unfortunately misses, I once asked Greg Lehey whether it would be possible to integrate on or modify vinum to do distributed RAID with another approach, but he didn't even answer to my mail) on another machine. Another solution, which I could also agree on using it, would be to have http://people.freebsd.org/~abial (Spy) to log all writes to the filesystem and simply copy all the modified files over the LAN (using rsync, scp or even NFS). What definitely doesn't work on most webservers (not on shared ones, anyway), is offline replication like standard rsync or cpdup as those take about 1h to simply check and update the twin of a 5 GB server which is not what I consider to be realtime (basically, I could agree on using any solution that doesn't create more than a 10 to 15min lag, even on big mailservers with hundred of thousands of files and dirs). Best regards, Gabriel [1] Having spend serious time looking into all available load balancing and fail over systems, I found that only NAT is a practicable way for a whole server farm. If you just need to have fail over for two servers, some IP takeover method is fine (if you can implement it properly which isn't as easy as it looks in first place, BTW). If you don't really need redundancy, you could simply use round robin DNS. -----BEGIN PGP SIGNATURE----- Version: PGP 6.5i iQEVAwUBO16Hq8Za2WpymlDxAQHtCwf+I/2P96LQxyRCyGYNIUKky/ndGenLBdFs 6fS7E1ahPF9tfjzvqmHPprEkfJgKNBpc2u7mxvZARA/PLyc7AdhnD8Cx1hltPqFV VJWuI+vDDO1fxB2ab6OnFadziDFm7O+eg7STMn0CfE5GAf5pijiHQAjzxZye5umx mBPNiYyF2CxOQwgd2pS/aQWdpOxHuBZqzzxjDp184Y+aNDFC4ATPUqbnzUJe6H0A MJ2p4hFePEi5ZKH1pH0RruBAjW1QGmcTmYvKgMm+w4azpGJQbvjvVHM4SfJ9wekc R5R++PTVgKB8e/yawcCIlTKngAhV6x5H/yWexzFi/WEMEgik/OFoXg== =BPWx -----END PGP SIGNATURE----- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message
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