LinuxQuestions.org
Review your favorite Linux distribution.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Software
User Name
Password
Linux - Software This forum is for Software issues.
Having a problem installing a new program? Want to know which application is best for the job? Post your question in this forum.

Notices

Reply
 
LinkBack Search this Thread
Old 02-07-2006, 04:06 PM   #1
homa2001
LQ Newbie
 
Registered: Feb 2005
Location: Madison, WI, USA
Distribution: SuSE, Red Hat
Posts: 22

Rep: Reputation: 15
Question Clustering two servers


I hate to do this, but I could not find a definite answer to my question anywhere so far.
I have done quite a bit of a research on clustering, but from what I have read, I understand that there should be "main" node that manages the load.

I guess it can be more clear if I explain my goal.

I have two identical servers, where powerful (just bought from Dell). I need to cluster them together, so they would look like one server a the user. I am planning on to run web hosting of it ( and there will be another pair for mail hosting). But I feel kind stupid devoting one out of the two for managment.


Please, advice wich clustering solution does not require a central node to manage the load. I do not care how the clustering is done, either its a DNS round robin, or just a process migration, or etc.

Ideally I want to distribute the load between two server that run apache and sync with each other all the time hosting directories, mysql db, etc (same for two qmail servers)

And what ever solution you recomend, please say if it supports adding a new node to the cluster later on (lets say in a half a year)

Thank you so much for you help in advance.

 
Old 02-07-2006, 06:20 PM   #2
stress_junkie
Senior Member
 
Registered: Dec 2005
Location: Massachusetts, USA
Distribution: Ubuntu 10.04 and CentOS 5.5
Posts: 3,873

Rep: Reputation: 331Reputation: 331Reputation: 331Reputation: 331
First I want to say that you may not need a cluster. You can have two web servers with the same name but different IP addresses. The DNS server has both IP addresses in its database with the same name attached to each. The DNS server will then alternate between the two IP addresses when it is queried about the common name. That is a kind of load balancing called round robin. It's simple but it does not take the load on each node into account.

There are several different kinds of clusters. The kind of cluster that has one controlling computer and the rest are slaves is called a Beowulf cluster. Another kind of cluster is a grid of computers that can send jobs to each other. Open Mosix is a good implementation of this kind of cluster. It has excellent tools to monitor all of the nodes in the cluster and all of the jobs running and queued in the cluster. Another kind of cluster does load balancing and provides continuous service if one node stops working. This is a high availability cluster.

Here are some web pages that should be interesting to you.

http://www.linux-ha.org/HomePage

http://en.wikipedia.org/wiki/Computer_cluster

http://sources.redhat.com/cluster/

Last edited by stress_junkie; 02-07-2006 at 08:55 PM.
 
Old 02-08-2006, 01:43 AM   #3
homa2001
LQ Newbie
 
Registered: Feb 2005
Location: Madison, WI, USA
Distribution: SuSE, Red Hat
Posts: 22

Original Poster
Rep: Reputation: 15
I would prefer the DNS round-robin way, but how do they syncronize? I want so those servers would be also transparent to the users who upload the files, so if the upload it to one, the changes should immedeately be synced with the other one (and later if I add more nodes with all of them)

Thanks,
Andrey
 
Old 02-08-2006, 05:09 AM   #4
stress_junkie
Senior Member
 
Registered: Dec 2005
Location: Massachusetts, USA
Distribution: Ubuntu 10.04 and CentOS 5.5
Posts: 3,873

Rep: Reputation: 331Reputation: 331Reputation: 331Reputation: 331
Having two web servers that were not clustered would only work if the web site was read only. If they have to share files that are updated by the users then you would have to look at a shared file system. NFS or SMB access to files on a file server would be the easy to implement solution there.
 
Old 02-08-2006, 09:51 AM   #5
homa2001
LQ Newbie
 
Registered: Feb 2005
Location: Madison, WI, USA
Distribution: SuSE, Red Hat
Posts: 22

Original Poster
Rep: Reputation: 15
Right, so with that being said, that means that both of that should be up all time, if I understand right what you are trying to say about NFS or SMB (or at least the NFS/SMB server one). Which destroys the purpose of having mirrored servers. I could probably right a scrip that runs every min and sync 'em, but that is ugly. I would still go with clustering, but do not know what would suite my needs the best.


 
Old 02-08-2006, 01:40 PM   #6
stress_junkie
Senior Member
 
Registered: Dec 2005
Location: Massachusetts, USA
Distribution: Ubuntu 10.04 and CentOS 5.5
Posts: 3,873

Rep: Reputation: 331Reputation: 331Reputation: 331Reputation: 331
Coincidentally I suggested exactly what you are looking for to someone else recently. You probably would like to have a look at EVMS in a high availability cluster environment. Here is some information.

http://evms.sourceforge.net/install/cluster.html
 
Old 02-08-2006, 02:57 PM   #7
homa2001
LQ Newbie
 
Registered: Feb 2005
Location: Madison, WI, USA
Distribution: SuSE, Red Hat
Posts: 22

Original Poster
Rep: Reputation: 15
Sorry for being annoying, but I kindof was seeing a system consiting of two servers, that would sync everything (if that is possible of course) so it would be transparent even for me, when I create a new hosting user or a new email account, ideally, even if I install or recompile new software i want to do it only once not twice or 3 times ( if I have 3 servers in a cluster).

I read about evms a little bit, and it looks like there has to be a separate server (in my eyes a single point of failure) where user data must be stored.

So my view of desired system is some kind of engine (or kernel mod) that runs on both servers and let them sync changes to each other like domain controllers do in M$ and a DNS server with round-roding algorythm would do that load distribution.

Hope that would make it clear

PS I am now starting to think that I should bring up some sort of domain controller, so I would create a user in the directory service and other linux server joined to the 'domain' would get the user changes, but still need to sync the user space.

Thanks,
Andrey


PSS Looks like Linux-HA has come very close to what I need, I will continue to read and search...

Last edited by homa2001; 02-08-2006 at 03:34 PM.
 
Old 02-08-2006, 03:21 PM   #8
fouldsy
Senior Member
 
Registered: Jan 2002
Location: St Louis, MO
Distribution: Ubuntu
Posts: 1,284

Rep: Reputation: 47
OpenLDAP could be used as your directory services system, which allows you to provide an LDAP master and then replicate the structure to LDAP slaves at regular intervals in the same manner MS DC's sync AD structures between each others. This would replicate the new user accounts or account detail changes across your servers and any new servers you add-in once you configure them as an LDAP slave.

As for sync'ing the actual data across servers, your idea of a simple rsync script or similar is probably the way to go and not really a dirty solution at all
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Clustering.... pastordan Linux - Newbie 4 01-30-2006 08:30 AM
clustering Ammad Linux - General 1 08-11-2005 08:05 AM
clustering rrecchia Linux - General 1 08-09-2005 01:29 PM
Clustering anand_rhce Linux - Hardware 0 12-15-2004 06:01 AM
Clustering Stephanie General 5 01-29-2004 12:04 AM


All times are GMT -5. The time now is 10:49 AM.

Main Menu
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration