The VAST Cluster compute load is designed to be balanced across all of the CNodes. VAST Cluster features a DNS server that can handle virtual IP distribution and simplify DNS administration. The DNS server returns a single virtual IP per query and is automatically updated of virtual IP pool changes.
There are several ways to use the DNS server. It is also possible to configure virtual IP distribution on your external DNS server. There are several advantages to configuring virtual IP distribution through the VAST Cluster DNS server.
You can choose to configure DNS-based virtual IP distribution in either way:
Using VAST Cluster DNS. In which DNS queries for subdomains are forwarded via an external DNS server to a single domain and queries are distributed to specific virtual IP pools according to subdomains.
Using an external DNS server. In which DNS queries are forwarded by an external DNS server to all virtual IPs and the client randomly selects a virtual IP.
VAST Cluster DNS
In this configuration, the DNS virtual IP responds to A-record requests for the DNS VIP for each subdomain and distributes those requests among the virtual IPs in that pool.
To set this up, do all of the following:
Decide on:
A domain suffix that will be common to all FQDN(s) that clients will use to request cluster access. For example: cluster.mycorp.com.
One or more short domain names which you can set per IP pool as subdomains. The domain suffix will be appended onto each domain name to form an FQDN.
For example: If the domain suffix is cluster.mycorp.com and the short domain names are domain1, domain2 and domain3, then you will be able to forward requests for domain1.cluster.mycorp.com, domain2.cluster.mycorp.com, and domain3.cluster.mycorp.com each to a different virtual IP pool. You'll only need one DNS delegation for cluster.mycorp.com which will forward all of the above FQDNs to the VAST DNS server.
Create a separate virtual IP pool for each set of virtual IPs that you want to place in a different domain. See Managing Virtual IP Pools.
Tip
You can also restrict view access to specific virtual IP pools via the view policy.
In each such virtual IP pool, set the VIP Pool Domain Name to one of the short domain names you chose. If the virtual P pools are already defined, modify the virtual IP pool to add a subdomain name in the VIP Pool Domain Name field.
Note
The VAST Cluster DNS server requires the domain name to be set on the virtual IP pool(s) even if you do not need more than one subdomain. You can set the domain name to be the same in more than one virtual IP pool if needed.
Configure the DNS server. Set the DNS Service Suffix to be appended to each of the domain names set for the virtual IP pools.
On the client DNS server, configure a single DNS delegation record. The DNS delegation record should forward any client requests for domains with the domain suffix that is specified as DNS Service Suffix to the VAST Cluster DNS Service IP. For each request for a specific subdomain, the VAST Cluster DNS server will return a virtual IP from the pool associated with the subdomain.
Example
Suppose:
There are two virtual IP pools: pool1 and pool2.
In the virtual IP pool configuration of pool1, the VIP Pool Domain Name is set to domain1.
In the virtual IP pool configuration of pool2, the VIP Pool Domain Name is set to domain2.
In the DNS server configuration, the DNS Service IP is set to 1.2.3.4, while the DNS Service Suffix is set to cluster.mycorp.com.
On the client DNS server, a single delegation record forwards all requests for cluster.mycorp.com to the IP 1.2.3.4.
This configuration can:
Resolve domain1.cluster.mycorp.com and return a single virtual IP from pool1
Resolve domain2.cluster.mycorp.com and return a single virtual IP from pool2
Client-Based Random Virtual IP Distribution with External DNS Forwarding
Configuring the VAST Cluster DNS server is optional. The alternative is to configure all DNS forwarding on an external DNS server. You do this by configuring delegation records to forward client requests for the VAST FQDN to all the virtual IPs configured on the cluster. In this case, your DNS server responds to each query with all CNode virtual IPs. The client randomly selects one of the IPs.
If you choose this option, you need to ensure that your DNS server is updated whenever any change is made to the virtual IP pools on the VAST Cluster.
The following table summarizes the differences between using the VAST Cluster DNS server to distribute the compute load vs using an external DNS server to distribute the load.
VAST Cluster DNS Server | External DNS Server | |
|---|---|---|
# IPs returned per DNS query | One IP. Client does not select IP. | All IPs. Client selects IP. |
How is the DNS server updated of changes in virtual IP pool ranges? | Automatically | Manually |
Ability to create a single-DNS delegation record as well as separate 'sub-records' for several virtual IP pools WITHOUT needing to create additional DNS records on the external DNS server? | Yes | No |