This blog post is the third part of a series about questions you may have wanted to ask about Netezza networking. The first part concentrated on basic Netezza networking, while the second part continued with network bonding and floating IP addresses. This is the third part, which concentrates on advanced configuration options.

Network speed

By default, a Netezza appliance host has two available Peripheral Component Interconnect (PCI) slots for additional PCI cards. Normally you would use one for a 10 GB dual port Network Interface Adapter (NIC) and the second available slot for dual port 8 GB Host Bus Adapters (HBA). The first you could use for 10 GB networking, and the second could be used for Storage Area Networking (SAN) or LAN-Free backups.

Internally, the appliance uses 10 GB networking. Externally, the default is 1 GB. If you want to have 10 GB external networking, then you need to have the additional 10 GB dual port NIC. Assuming you have a 10 GB network infrastructure in place, you most probably want to go directly to 10 GB.

Even if you plan to initially start with 1 GB external networking, you should consider getting the additional 10 GB NIC and 8 GB Host Bus Adapter (HBA), because you are likely going to use them later.

More about network bonding

By default, the appliance has two hosts. Both of the hosts have one external bonded virtual network device, which consists of two physical 1 GB network interfaces. By default, the network bond is created as active/passive, so the maximum bandwidth you can achieve is 1 GB. If you ask, and your network switch supports link aggregation, you can configure the network bond as Active/Active to get a 2 GB link.

As mentioned above, there are two available PCI slots. This means you can also add two 10 GB dual port NICs to those slots. That way, you can bond up to four 10 GB physical network devices together to achieve maximum 40 GB bandwidth.

Another option would be to use two of the 10 GB ports for virtual IP addresses for application connectivity, and the two remaining ones for a backup network. There are plenty of options, when you consider that you can bond together any of the 10 GB ports in any order to create a bonded device, and then you can choose to go for active/active or active/passive mode.

What about LAN-Free?

This section doesn’t actually cover pure TCP/IP networking, but rather connectivity without TCP/IP. As mentioned earlier, you can have 8 GB HBA installed on one or both of the available PCI slots on the hosts. If you decide to have at least one available PCI slot for additional 8 GB HBA, you could use it for LAN-Free backups.

TCP/IP networking is usually done in shared mode, so you have to share the bandwidth with other users—unless you have a dedicated link, which most often you don’t have. With SAN it is easier and more common to create a dedicated link between the appliance and, for example, the backup server. Or you can connect to an external SAN disk through a dedicated link. That of course has clear benefits; when you know exactly how much bandwidth there is and when you don’t need to share it with anyone.

Another benefit with the LAN-Free option is is the CPU usage. TCP/IP implementations tend to have more CPU overhead compared to SAN. I would emphasize the benefit of the dedicated link though, since CPU on the host is rarely limited while dealing with backups, for instance.

Management interfaces

I already mentioned the management IP addresses: usually two per host, one being the host IP itself, and the other being the IP address of the integrated management module (IMM).

The IMM IP addresses are extremely handy if the host itself is not reachable through the host IP due to the fact it has failed with a hardware error, or if there is something wrong with the configuration. Through IMM, you get console access though the web interface, and either debug the problem or fix the configuration issue.

Some clients require a separate management IP, which is not attached to any network devices used by applications and which still has direct TCP/IP connectivity to the host. In this case neither the host IP nor the IMM IP can be used; you need to use some other available physical network port or interface. If this is the case, you should clearly define the requirements, so you can check the available options.

What else?

If anything else is on your mind that you did not dare to ask earlier, feel free to ask or comment below. You can also follow me on Twitter @TVaattanen to discuss more about Netezza.

This blog post is the second in a three-part series with the goal of answering questions you might have about Netezza networking. The first part concentrates on basic Netezza networking, whereas this second part covers more advanced networking concepts. For advanced configuration options, you can check out the upcoming third part of this blog post.

Network bonding

You have two hosts: active and passive. Each has its own IP address. These IP addresses are not floating. These are called host IPs. Since you want to have maximum redundancy on all components, there are actually two physical network devices virtually bound together to create virtual networking devices (one for each host). Both hosts have two physical network devices that carry one IP address. This is called network bonding.

Let’s say both of the hosts have network devices eth6 and eth7 and they create a coupled virtual device called bond2. We usually use bond0 and bond1 internally, so the first bonded device for external use is normally bond2.

For the virtual device bond2, you can assign an IP address and connect to a host. Both active and passive hosts will have this device and both of the hosts will have their own individual IP address, which is bound to this virtual device.

Virtual IP

If you think of this from an applications point of view, it wouldn’t make sense to connect to the host IP, since if the active host fails, you would need to re-configure applications to use the new active host, which has a different IP.

That’s why applications use virtual IP. Virtual IP is actually an IP alias, which is bound to an active host. Hosts run standard Linux operating systems, so if you are familiar with Linux, it’s easy to explain. If not, it’s still not rocket science. On Linux, you can easily add IP aliases on top of any physical, or virtual for that matter, network device . If you have physical network device eth0 with fictional IP address 192.168.1.100, you can add another IP address to that same physical device just by assigning an IP to device eth0:0. Next you add to device eth0:1 and so on.

In this case, you have virtual network device bond2, which is a bonded device having physical devices eth6 and eth7 behind it. If you lose eth6, you are still good as long as physical device eth7 is good. To connect to either of the hosts directly, you would use the IP address assigned to bond2 on the particular host, or rather the host name you have assigned in your domain name server (DNS) for that IP address.

Floating IP

As I said, applications connect to a virtual IP. The virtual IP is assigned to virtual network device bond2:0. It only exists on an active host. This is something called a floating IP, and it is always on the active host. If Host 1 fails, it will be on Host 2. If, as in my example, device eth6 fails, you have bonded device bond2, which consists of eth6 and eth7, the floating IP is still good on that same appliance as before.

There are two virtualization layers here. One is done though network bonding, the other is done through cluster software. If one of the network devices physically breaks, the network bonding will do the trick, and you are still good to go. If the other appliance breaks, you have clustering software, which can deactivate the bond2:0 on the failing host and create bond2:0 on new active host.

So the bond2:0 always has the virtual IP your applications are able to use. You should, of course, always assign host names in your DNS for this virtual IP, and use this host name in your applications instead of using IP addresses directly. That way, if you ever need to change the IP address for the virtual IP, you don’t need to change configurations for several applications. Instead, you just have to change the IP for the host name you have defined for the virtual IP in your DNS configuration.

What about changes to the default configuration?

I will cover advanced configuration options in part three of this blog post. If you have any network-related questions or suggestions, please add them below in the comments. You can also follow me on Twitter @TVaattanen to discuss more about Netezza.