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High-availability, load-balancing, fail-over?

Discussion in 'Data Protection' started by pthirose, Apr 19, 2010.

  1. pthirose

    pthirose Member

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    After an afternoon's reading of forum posts dating back a few years, I don't see a particularly definitive answer on this. Perhaps, once my cPanel purchase is finalized, I can get official/definitive support/answer :)

    First, my understanding/assumptions:
    - I see WHM has move a user ability, and there is mention of both a pkgacct and cpbackup script. All of them, I gather, will backup and restore "everything" related to a particular user - files, permission settings, email, mysql database, wordpress entries, etcetcetc.

    - cPanel requires a license per IP address. If I were to provide HA/LB across two active/active cPanel servers, I'd need two cPanel licenses.

    My fairly basic questions

    1. If I use Linux LVS-DR, that requires the VIP to be present on all realservers. Can I purchase a single cPanel license tied to the VIP? Since I'd be serving all the same contents from all my realservers, would this be a problem? I don't mind buying a cPanel license for all my realservers and tying the license to each RIP instead. But the problem with doing that, I think, is each cPanel would respond to its RIP rather than a VIP and load-balancing wouldn't be -DR anymore, but maybe a -NAT type?

    2. Are there better, more real-time-ish ways to backup/copy user data from one cPanel host to another? I could cronjob the pkgacct, or cpbackup. I could have my support staff manually do a copy user at the beginning of every shift, etc. But I'd rather have a way to have it a bit more realtime.

    3. After (however it's done) copying a user's settings, files, databases, etc to another cPanel system, does the second cPanel system talk to its own MySQL database? For example, client A on server A has mysql database A running on mysql daemon hosted on server A. I copy user A to server B. Now server B has user A with mysql database A on the mysql daemon running on server B. And if I were to hit user A's website on server B, it would utilize the local database on server B, right? So the pkgacct or cpbackup or move user in WHM all are able to not only copy everything over, but make changes to the material being copied over to make local references? I don't expect it to go through my blah.html file and change any ahref links (say if I had it hardcoded to .../serverA/blah2.html).

    I'm ok w/it being say a "primary" cPanel system and a bunch of "slaves" to share the load, so to speak. If the Mysql DB is separate from all the cPanel hosts, and say its own Mysql cluster (or replicated master/slave - I realize beyond the scope of this particular forum), would this work? I don't know what other resources that cPanel users and/or websites would write to. If I do have multiple cPanel hosts, I of course want writes to one, to be reflected to all.

    Not quite fully HA/LB, but does/can cPanel insert a session/cookie or whatever type thing that an external LB could detect and use to "sticky" a session/connection to the same cPanel server? If I have the proverbial shopping cart that I start on serverB, I want to make sure that the rest of my connections from my web browser go to serverB. I suppose this should rightfully perhaps be handled at the shopping-cart/website application level rather than at the cPanel level, but I thought I'd ask.

    If I take out the active/active LB part out of this, and only run active/passive HA, would the above become easier? I could copy everything from active A to passive B every ## amount of time. passive B would have a different IP address than active A. So when A goes down, I can either reset passive B to assume active A's IP address (probably the easiest/fastest) or I could have our firewall/router send all traffic destined for the now-dead-A's IP address to server B's IP address.

    I'd obviously prefer an active/active HA/LB scenario. But we're more interested in HA than LB, if we had to choose.

    I realize this is similar to all the "cloud" type scenarios and other questions on this forum. We do have full/root access to our entire pool of cPanel servers. We can (but haven't at this time) setup a pool of MySQL servers for HA/LB purposes. They do all have access to the same SAN.

    Thank you,
    PH
     
  2. Spiral

    Spiral BANNED

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    Reading through all your post comment, I can definitely answer all your technical questions and also help point you in the correct directions. However, I suspect in this particular case that an appropriate reply would be quite lengthy as some the topics you asked are quite advanced and each line item point can be a somewhat in depth and lengthy discussion in itself which gets even more complex because Cpanel's support in this particular area is still very much limited so there is a lot of additional considerations and obstacles to overcome regarding all of this and also in regard to thinking about technical implementations.

    As such, it might be a whole lot easier to take this topic to chat or email
    and to that point I am sending you my direct contact information and feel free to try to catch me on any of those.
     
  3. cwalke32477

    cwalke32477 Well-Known Member

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    I'd be interested in seeing this discussed on the forum, as I think it would be valuable community information.
    PH has a very valid idea. It would be a shame to keep it all locked away in private messages and emails.
     
  4. Spiral

    Spiral BANNED

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    Generally speaking the topic is quite involved and there is already several discussions on going in other topic threads around here so might be redundant to expand those conversations into yet another thread.

    Specifically speaking, any solution for this user would be a "custom" solution to their own unique situation and probably of little value to anyone else which unfortunately would be a necessity since Cpanel has no officially supported avenues for any kind of failover or HA at this time.

    Many solutions are not very cost effective and those would not be very viable for many hosts unless you have a very deep budget to expend and that is also another consideration as well.

    For the latter group, I might recommend something more along the lines of remote off site backups or a cloud hosting type solution where the entire server can be re-deployed elsewhere to another machine very rapidly minimizing any downtime in worst case scenario events.
     
  5. benw01

    benw01 Registered

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    I'm interested in this topic too. As far as I can tell, there's no facility for load-balancing or HA built into cpanel.

    Similar to the OP, our current infrastructure is a load balancer device in front of a bunch of apache servers, which mount their data and config from an NFS share, thus making the apache servers identical config- and content-wise. Thus the load balancer can direct traffic to any of the apache servers and get the same responses.

    Does cpanel support a configuration like this?

    - Ben
     
  6. cPanelJared

    cPanelJared Technical Analyst
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    cPanel does not provide any support for any type of load-balancing system. cPanel is not "aware" of this type of setup, and no consideration is built into the product for this.
     
  7. cPanelDavidG

    cPanelDavidG Technical Product Specialist

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    At the 2010 cPanel Conference, one of our guest speakers discussed using VMWare solutions to create VPSs that spanned multiple physical servers and handled HA and all that at the virtualization layer. Since it looks like a regular VPS to cPanel&WHM, the software works well with it. That may be something to consider.
     
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