Riccardo Riva

Posts Tagged ‘Networking’

In this post I am going to talk about a very particular piece of hardware, unique on the market at this moment and that should be very useful for virtualization or clustering purpose, with a very low budget.

This product is called DamVirtualOne.

DamVirtualOne is a modular server (not a Blade) and have some very interesting feature :

- Fully redundant hot swap power supply.
- Fully redundant hot swap Gigabit ethernet switches with failover.
- Fully redundant hot swap storage controller, with multipathing and failover support.
- Up to six (6) compute module double socket (for Intel Xeon 5400 or 5500 CPU family).
- Up to 96GB of RAM each compute module.
- Up to 14 HDD SAS.
- Up to two redundant external SAS connection to storage expansion or SAS device connection (i.e. Tape Unit).

But the more important things that lead me to write this post is that storage is shared between the compute module, but not as other Blade Server on the market right now, with DamVirtualOne you should create a Virtual Disk (similar to a SAN LUN) and share it between all compute module if you need it.

At this time only IBM Blade Center S should have the same possibility, but it’s a Blade server, not a modular server, and there is a big price difference.

I had the luck to test the DamVirtualOne for few days (a lot) and I’ve installed the following :

- VMware ESXi 3.5
- VMware ESX 3.5
- Red Hat Enterprise Linux 5.3
- Microsoft Windows Server 2003
- Microsoft Windows Server 2008

I’ve created some fully function, and very performance VMware HA and DRS Cluster, and some Linux Cluster based on RHEL, and a large number of my previous post was written based on the installation above.

The standard server virtualization or clustering best practices require shared storage to use all benefits of the technology and this lead to buy SAN, Storage array (tipically Fibre Channel) who is very expensive, difficult to maintain and create a very complex infrastructure.

So you should know why I’m so excited about DamVirtualOne, because it’s a “single package” that contains all things you need for virtualization or clustering purpose : servers, storage and network a real datacenter all in one.

With the maximum configuration this machine should support up tp two hundred (200) Virtual Machine !! And his price will be very similar to two or three phisical server (as you are useful to see) and a shared storage, so you should understand that is a beautiful “piece of iron”.

I truly believe that modular server is sometimes under valuated, but in my opinion there is an enormous potential in it and it will be beautiful if this post lead some people to find out a solution, cheaper than other more famous one, using this piece of technology.

You should found more details about DamVirtualOne at the following websites.

http://www.damvirtualone.it

Feel free to ask, they will answer you !

Riccardo

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The following is some Networking Stuff about VMware ESX networking.

You could also find all these information on VMware WebSite but I like to keep some info also here for personal quick reference.

Virtual Ethernet Adapters

There are three types of adapters available for virtual machines :

1. vmxnet is a paravirtualized device that works only if VMware Tools is installed on the Operating System. This adapter is optimized for virtual environments and designed for high performance.
2. vlance emulates the AMD Lance PCNet32 Ethernet adapter. It is compatible with most 32-bit guest operating systems and can be used without VMware Tools.
3. e1000 emulates the Intel E1000 Ethernet adapter and is used in either 64-bit or 32-bit virtual machines.

There are two other virtual adapters that are available through VMware technology. Vswif is a paravirtualized device similar to vmxnet that is used by the VMware ESX service console. Vmknic is a device in the VMkernal that is used by the TCP/IP stack to serve NFS and software iSCSI clients.

Virtual Switches

VMware technology includes virtual switches that you can build on demand at run-time to provide different functions, including:

1. Layer 2 forwarding.
2. VLAN tagging, stripping and filtering.
3. Layer 2 security, checksum and segmentation offloading.

This modular approach reduces complexity and maximizes system performance, VMware virtualization technology loads only those components it needs to support the specific physical and virtual Ethernet adapter types used in the configuration. Additionally, the modular design enables VMware and third-party developers to incorporate new modules to enhance the system in the future. Up to 248 virtual switches can be created on each VMware ESX host. Following are important features of virtual switches:

• Virtual ports: The ports on a virtual switch provide logical connection points among virtual devices and between virtual and physical devices. Each virtual switch can have up to 1,016 virtual ports, with a limit of 4,096 ports on all virtual switches on a host. The virtual ports provide a rich control channel for communication with the virtual Ethernet adapters attached to them.
• Uplink ports: Uplink ports are associated with physical adapters, providing a connection between the virtual network and the physical networks. They connect to physical adapters when they are initialized by a device driver or when the teaming policies for virtual switches are reconfigured. Virtual Ethernet adapters connect to virtual ports when you power on the virtual machine, when you take an action to connect the device or when you migrate a virtual machine using VMware VMotion. A virtual Ethernet adapter updates the virtual switch port with MAC filtering information when it is initialized or when it changes.
• Port groups: Port groups make it possible to specify that a given virtual machine should have a particular type of connectivity on every host, and they contain enough configuration information to provide persistent and consistent network access for virtual Ethernet adapters. Some of the information contained in a port group includes virtual switch name, VLANIDs and policies for tagging and filtering, the teaming policy and traffic shaping parameters. This is all the information needed for a switch port.
• Uplinks: With VMware technology, uplinks are the physical Ethernet adapters that serve as bridges between the virtual and physical network. The virtual ports connected to them are called uplink ports. A host may have up to 32 uplinks.

REFERENCE: http://www.vmware.com/files/pdf/virtual_networking_concepts.pdf
Hope this help

Bye

Riccardo

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Some times I had to use some tools to test the network to find some problems or simply to debug something not working fine.

Tcpdump is a popular computer network debugging and security tool which allows the user to intercept and display TCP/IP packets being transmitted or received over a network to which the computer is attached. Tcpdump allows to precisely see all the traffic and enables to create statistical monitoring scripts.

At an ethernet segment, tcpdump operates by putting the network card into promiscuous mode in order to capture all the packets going through the wire. Using tcpdump we have a view on any TCP/UDP connection establishment and termination.

Obviously, if you can mirror one or more port on the network devices to the port on which your computer is connected you’ll obtain a lot more data.

Some examples:

all packets arriving at or departing from 192.168.1.1
# tcpdump -n host 192.168.1.1

To print traffic between 192.168.1.1 and either 10.0.0.1 or 10.0.0.2:
# tcpdump -n host 192.168.1.1 and \( 10.0.0.1 or 10.0.0.2 \)

To print all IP packets between 192.168.1.1 and any host except 10.0.0.1:
# tcpdump ip -n host 192.168.1.1 and not 10.0.0.1

To print all traffic between local hosts and hosts at Berkeley:
# tcpdump net ucb-ether

To print all ftp traffic through internet gateway yyy:
# tcpdump ‘gateway yyy and (port ftp or ftp-data)’

To print traffic neither sourced from nor destined for local hosts (if you gateway to one other net, this stuff should never make it onto your local net).
# tcpdump ip and not net localnet

To print the start and end packets (the SYN and FIN packets) of each TCP conversation that involves a non-local host.
# tcpdump ‘tcp[13] & 3 != 0 and not src and dst net localnet’

To print IP packets longer than 576 bytes sent through gateway yyy:
# tcpdump ‘gateway yyy and ip[2:2] > 576′

To print IP broadcast or multicast packets that were not sent via ethernet broadcast or multicast:
# tcpdump ‘ether[0] & 1 = 0 and ip[16] >= 224′

To print all ICMP packets that are not echo requests/replies (i.e., not ping packets):
# tcpdump ‘icmp[0] != 8 and icmp[0] != 0″

Hope this help

Bye
Riccardo

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