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  1. #1

    Email Server Cluster - Over 2 / 3 VPS's

    Hi Guys,

    Was thinking about running an email server for some local businesses, so they can out source their IT systems (cheaper).

    Now setting up a mail server, say running DirectAdmin is normally fine.

    However this is a "mission critical" service to these guys, so I want 9.9999% uptime !

    I was thinking of getting a few VPS's around 384MB RAM, 20GB HDD spec in the same DC but on different nodes and setting up a cluster...

    And then I thought..... How the hell do I do that..? WHT must know.....

    So I am simple asking if there is any guides out there, or any experts on this matter that might want to help.

    Thank you

  2. #2
    Join Date
    Apr 2002
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    I don't know about setting up Directadmin specifically for this but I guess it's doable.

    What you might want is a load balancer or 2 for redundancy, and multiple smtp, pop servers behind it, so you or clients only connect to 1 IP for pop,imap and 1 for smtp maybe. The load balancer sorts out where the connections really go to (heartbeat + lvs)

    Then you need a mailstore, or 2 redundancy, that the pop,imap server(s) mount the mail directories onto.

    There's a thing called dbmail that stores all mail within a database too, that you can replicate, but I wouldn't recommend that based on experience with it..

  3. #3
    Hi Steve,

    Thank you for your post.

    Is there a way to do it without a load balancer, as these are quite expensive I believe.

    Thanks

  4. #4
    Join Date
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    A load balancer needs only to be a linux box (or VPS) running heartbeat and lvs.

    If you want seemless redundancy, then that is what you need, else you'd have to change your mail host when a box went down, to connect to pop, imap, smtp etc - which I don't think from your post you wanted.

  5. #5
    Ah ha,

    I like the sound of a VPS load balancer, I didn't realise that was possible, how hard will it be to setup something like this.

    Say:

    | VPS - 1 (Load balancer )
    |
    |--- VPS - 2 Running mail server
    |--- VPS - 3 Running mail server
    |--- VPS - 4 Running mail server

    But that still leaves a single point of failure (the load balancer) what about a second load balancer..?

    Alos what kind of hardware spec per VPS would I need for say 100 mail boxes but scalable to 500ish.

    Thanks

  6. #6
    Join Date
    Aug 2002
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    Bharat
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    What if this load balancer linux box goes down?
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  7. #7
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    You can have 2 load balancers running heartbeat + lvs and they will monitor each other, if one goes down, then the other takes over - but you are better to have physical hardware rather than VPS's then, as you are better to use a serial port to connect them together (having 2 vps's on 1 node using virtual serial I guess is possible, but you wouldn't want to do that for 99.99999% uptime)

    You have 3 mail servers, which is all good, but as you grow you might want to make them either pop/imap or smtp only servers.

    I wouldn't personally do this with VPS's - I'd give each server 1GB of ram, a P4 cpu and run 2 x pop/imap and 2 x smtp.

    The load balancer can have as little as 256MB or less even.

    You will want a decent file server however, I'd go dual proc for that and plenty of ram.

    You can do it cheaper, but for the uptime figures you are quoting, that's what I'd say. What are you going to use if the network goes down?

  8. #8
    Thats a fairly hefty spec.

    I want to see if it possible first, so I will setup it up in the lab first, before thinking about putting it into production.

    You said about a file server, would you have that as a store for all the VPS's / email server e.g. no actual data is stored on them, instead straight to a file server?

    Thanks

  9. #9
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    Yes you will need a file server, the pop, smtp servers will mount the files via nfs I'd imagine, as if you have more than 1 pop server, they both need to be able to get to the files, and if 1 pop server is down and it hosts files, then your users can't get mail.. and if your file server is down.. and so on

  10. #10
    Join Date
    Aug 2003
    Location
    Kansas City
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    placebo, a little outdated LocalDirector can be obtained from ebay really cheap, and it should do the job as you described. LDir-430 got 384MB RAM. You can use a serial cable to cluster two identical units of LocalDirector allow the LB failover. I'm currently doing similar things as you are doing. Instead of VPS, I got physical servers lined up ready do the lab test.

  11. #11
    Join Date
    Aug 2003
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    Kansas City
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    Quote Originally Posted by Dotable Steve View Post
    Yes you will need a file server, the pop, smtp servers will mount the files via nfs I'd imagine, as if you have more than 1 pop server, they both need to be able to get to the files, and if 1 pop server is down and it hosts files, then your users can't get mail.. and if your file server is down.. and so on
    Steve, your post is very interesting. I got some ideas about my setup (below), but wondering if you could shed me some lights if you'd do this for your web/email hosting? 1) 2 x LDir-430. 2) 2 x 24-port gigabit switch. 3) 7 x 1u boxes, each with 2xgigabit NIC, 2x36GB 10k SCSI drives hotswappable, dual xeon 2.4GHz. 4) 2 x 3TB Adaptec SnapAppliance with 2xgigabit NIC.

    Thanks in advance.

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