Multiple servers

ISOS6

ISOS6

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May 7, 2009
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Erbil, Tarin Hills, Iraq
On my first server is getting enough users. And have as usual ns1.domain.com and ns2.domain.com the current server.

How is that set up other server? I will also set up as the first? ns1 and ns2 or ns3 and ns4?
 
The easiest way to implement this is to remove ns2 from the first server and add it to the second server, and then setup multi-server option on your first server to add DNS to the second server, and on the second server to add DNS to the first server.

Jeff
 
Same thing, choosing two or three servers to be your authoritative servers. Generally no more than ten authoritative nameservers are practical, and usually there's no reason to have that many unless they're greatly geographically dispersed. Informative article from an O'Reilly networking book here.

But there's no reason you can't link them all.

We do something a bit different, we have two dedicated nameservers (they do nothing else), one in Germany, and one in California (USA), and we run our own Master2Slave DNS Replicator (search for it on these forums if you'd like) to keep them synchronized using standard BIND master/slave technology.

Jeff
 
As far as I can see, I responded to your question and explained how to do it. If I missed something please ask a specific question.

Jeff
 
Thanks for your reply. But the question is the following:

If I have 10 dedicated servers, how do I connect all together? The fact that everyone uses the same NS and DirectAdmin port.
 
I explained how to do the DNS. There's no way to have everyone log in through the same DirectAdmin login; each user must log in through his server's DirectAdmin URL.

Jeff
 
Almost answers my question

With numerous servers, we use the mutli-server options via the DA control panel. However, I ask has the means been developed - or is it in the works - to be able to send user/clients to one single URL to log in to DA (like ns.ourdomain.org), versus numerous URL's as servers become burdened? Example: it would be wonderful to be able to provide a secure login for user/clients at ns.ourdomain.org instead of ns1.ourdomain.org, ns2.ourdomain.org, etc. As Jeff mentioned, we have our "ns" nameserver in one datacenter and our "ns1" nameserver located at a different datacenter. But it's a wee bit of extra work to keep up with allocation of new clients to new servers. Which generates another question - and forgive me if I slept through that networking class and other symposiums - but how do the "big boys" offer Gigs and Gigs of storage for hosting, when I look at the capacity of current hard drives, crunch the numbers and can only wonder how the "big boys" offer 200Gb of storage per user (yes, I am aware of limitations for storage). So how do they do it?

Sloane<o>
 
To understand, how «big boys» do their hosting, please, see this illustration http://ispserver.com/ru/products/cloud_hosting/cluster.html It's a good example to understand an idea.

I think, you can do it yourself or hire somebody, in order to develop a program to manage a cluster under DA. The idea is that, you use one copy of directadmin for all of your users, and their data is located on a storage system.
 
zEitEr said:
To understand, how «big boys» do their hosting, please, see this illustration http://ispserver.com/ru/products/cloud_hosting/cluster.html It's a good example to understand an idea.

I think, you can do it yourself or hire somebody, in order to develop a program to manage a cluster under DA. The idea is that, you use one copy of directadmin for all of your users, and their data is located on a storage system.
Click to expand...

Mainly, you can spread the load by creating a loadbalancing cluster indeed. We've got experience with this but, the only part is the port that DA listens on. This is machine local and can't be reversed proxied (as far as I know).

Usually, we create the following situation. We use a product called the Citrix Netscaler, a loadbalancer that is either hardware or a virtual for Xen. This appliance can use it's reverse proxy method for fetching information from the backend (web and MySQL) servers.

It then reverse proxies it, and delivers the content to the end user.

In your situation, as Jeff already mentions, you just need DNS replication. Just use the multiserver setup, or set up an external (PowerDNS maybe?) slave. We use this for all of our customers. Each customer with an own servers gets NS1.hisdomain.ext and NS2.ourdomain.ext. This way, all of our clients won't have a SPOF in DNS.

When their local DNS falls out, they can use our second nameserver to still provide DNS lookups.
 
I'm not sure whether user turnersloane is writing about high availability, ease of allocation of new accounts, or just logins to DirectAdmin.

DirectAdmin is not designed for high-availability hosting, but rather for what I call utility shared hosting: every account is on a shared server with other accounts. If that server goes down, the clients on that server go down. The purpose of multiple DNS servers in this design is simply so that when the server is down the prospective visitor gets a "site not available" error instead of a "site doesn't exist" error.

While you can use DirectAdmin in a high-availability solution, it's neither straight-forward nor does it guarantee universal availability. And it can get expensive. You can use a load-balancing hardware solution, but then you need MySQL on a separate server or servers, with all the issues of replication, and if you need it, session management. The big guys can do this with multiple servers running one site, but it's close to impossible for you to monitor and manage it for your shared hosting clients. And there's still the possibility the load-balancing hardware will fail.

The difference between 99.9% uptime and 99.99% uptime is a total of 38.89 minutes per month, out of a total of 43,200 minutes in a month. That may be important to your client, but is it worth the money it takes to address it?

I've already addressed what I call the poor-man's solution previously in other posts on these forums, for use in an environment where there's either no database, or the database is used only to create content, and isn't changed by the visitor.

User tomtom901 has a good solution, but I'd bet he'd be the first to tell you it's not the kind of simple solution most of our shared hosting clients are willing to pay for.

Now to address ease of allocation of accounts to servers...

There really aren't any perfect algorithms for how to assign new clients. If your business is large enough that you have to worry about filling up servers rapidly enough to use some kind of automation you'd probably do best looking for solutions among the various billing/provisioning packages that work with DirectAdmin.

DirectAdmin must be licensed per hosting server, but licensing isn't required for DNS servers (unless you're using the DirectAdmin multi-user option for DNS replication) or for MySQL (because you won't be using DirectAdmin to manage MySQL databases on other than the account's shared hosting server.

Logging into DirectAdmin can be managed easily enough, and it's been discussed in these forums multiple times.

Here's one scenario:

Create your own DirectAdmin login page at for example, login.example.com where you'll handle logins for multiple servers with usernames one.example.com, two.example.com, and so forth.

On your login page ask for the domainname only. Do a behind the scenes lookup of the domainname's rDNS to get the server name, then dynamically create and return to the user's browser a link to the proper server where the user will enter his username and password. Simple, no proxies required.

I'd like to hope that user tomtop901 and I can work together on a loadbalancing scenario for those DirectAdmin users who require it, but I'm not sure it's a problem where DirectAdmin will turn out to be the proper solution.

DirectAdmin is great for what it's great for, but it's not the solution for every problem.

Jeff
 
Good answer, Jeff.

I still believe, Directadmin can be used with external storages. Thats how turnersloane can get Gbs/Tbs on HDD.
 
Thanks!

Yes, DirectAdmin can be used with external storage.

I didn't mean to imply that it couldn't. However today you can easily buy a server which will hold ten 2 TB drives; with 20TB of local storage you shouldn't need external storage, which generally is both slower and more expensive than external storage.

Jeff
 
where is the poor-man´s solution

Where is the poor-man´s solution, can't findit in other posts. i have searched unsucessfully.

Great post by the way.
 
Thanks. I may not have called it the poor-man's solution.

It only works for static sites and for sites not driven by customer input, because of limitations in replication.

It entails a second server running apache (perhaps also DirectAdmin for ease of administration). You only allow content and management changes on your Server #1, and manage updating to Server #2 using something as simple as automated backup/restore, more typically rsync and MySQL replication.

Each machine runs DNS for the site(s), each zone file pointing to it's own IP#, and with low TTL. When both machines are running, some visitors will hit each machine, depending on which DNS reply (from which machine) they get first. When one machine is down, only the other will serve, and it will only serve DNS for itself.

We can do much higher end solutions in our Los Angeles datacenter including fiber-channel SAN. But it's not cheap, and we don't consult on how you can do it; there are already lots of books and consultants available on the open market.

Jeff
 
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