<HTML><BODY> <table style="width: 100%" cellspacing="0" cellpadding="0"> <tr> <td valign="top"> Hi there, As far as the VM goes... I'd use KVM, mainly because RH is replacing Xen with KVM at some point in the future (last time i checked, it was going to be during the first half of 2009) :) I will think about the question regarding enabling of users to launch processes on remote servers that house the data being processed a little and get back to you with some info as soon as possible. Regards, Colin ________________________________________ From: <a href="mailto:redhat-sysadmin-list-bounces@redhat.com">redhat-sysadmin-list-bounces@redhat.com</a> [redhat-sysadmin-list-bounces@redhat.com] On Behalf Of Laurent Wandrebeck [lw@hygeos.com] Sent: 26 March 2009 12:49 PM To: <a href="mailto:redhat-sysadmin-list@redhat.com">redhat-sysadmin-list@redhat.com</a> Subject: Re: a couple questions from a cluster newbie Le lundi 23 mars 2009 07:47, Colin van Niekerk a écrit : > Hi there, Hi Colin, > > Apologies is anyone has answered this already and I have missed it. This > post has been out for a while now. You're the first, kudos :) > > I would configure three VM's on the Failover box and add the ability to > have each server failover separately. This would involve having three load > balanced clusters as in the attached, again fixed sized fonts. Thanks for your ascii art. Which VM would you advice ? Xen as it is officially supported on rhel, or kvm ? something else maybe ? > > To replicate data between the virtual server and the physical server within > each cluster I would use DRBD (RAID1 on a network level), you can configure > this so that only once the data is committed to disk on both sides does the > kernel confirm the write. This will present the system with a new block > device and data must only be read and written via this device. As long as > your system is 'strong' enough and the link between the servers is fast > enough (this would depend on the amount of changed to the data - how much > data would need to be written to the block device on the other end of the > network) it will be just like reading and writing to any other block > device. Our network is gbps, and machines will be in the same rack, one hop away. So I guess synchronous replication will do the trick. > > For the backend you could use Conga with luci and ricci to manage the > cluster (thinking about ways to avoid pain going forward) but I have not > done this in a production environment so I'm not sure about the details. OK, I'll set up a couple VM soon to check the details. > > I'm afriad I have worked very little GFS as well so I can't answer you on > that side of things. Maybe the GNBD would be better for the load balanced > server replication as well, but as far as I know the main reason you would > use GNBD is that it exports the file system to many users and manages > locking better between the users which wouldn't help in the pg/ds/ap > clusters. Can anyone confirm? > > Just so I'm clear on the backend side. It sounds like there is a level of > interaction between users and the actual data on the backend servers. Do > the users query a process on the storage/processing servers and then that > process works on the data and gives the user a result? Or do the users > interact with the data directly? Users interact directly with data. classic (and simplified) scheme is: (shell script pseudo code) for i in files_to_be_processed do processing_program $i $output_dir/$output_result done Thx for helping, Regards, -- Laurent Wandrebeck IT Manager / Directeur des systemes d'informations HYGEOS, Earth Observation Department / Observation de la Terre Euratechnologies 165 Avenue de Bretagne 59000 Lille, France tel: +33 3 20 08 24 98 <a href="http://www.hygeos.com" target="_blank">http://www.hygeos.com</a> -- redhat-sysadmin-list mailing list <a href="mailto:redhat-sysadmin-list@redhat.com">redhat-sysadmin-list@redhat.com</a> <a href="https://www.redhat.com/mailman/listinfo/redhat-sysadmin-list" target="_blank">https://www.redhat.com/mailman/listinfo/redhat-sysadmin-list</a> Colin van Niekerk Technical Mimecast South Africa Phone 0861 114 063 • Mobile +2782 557 9081 • Fax 086 522 6377 This email, sent at 22:10:17 on 2009-03-26 from colin.vanniekerk@mimecast.co.za to redhat-sysadmin-list@redhat.com has been scanned for viruses and malware by Mimecast, an innovator in software as a service (SaaS) for business. 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