Archive for December, 2012

XenServer, Hyper-V, and ESXi – Architecture, API, and Coding

Monday, December 24th, 2012

VirtualizationBelow is a link to the slide deck for a presentation I gave to some friends/colleagues for a Berkeley Virtualization and Cloud Computing certification course I took in early 2012. For my final project I did a XenServer, Hyper-V, and ESXi hypervisor comparison in regards to market share, architecture/installation, and APIs/coding. The project involved not only a presentation but coding for all three hypervisors – XenServer, Hyper-V, and ESXi. Technical details, demos, and coding examples are provided in the presentation. You can also download all code from either the download section of this site or for the latest code updates download from GitHub. (more…)


Dell Force10 – Layer 2 Multipathing via Virtual Link Trunking (VLT)

Tuesday, December 18th, 2012

In this blog I use one Dell Force10 S50N [FTOS] and three Dell Force10 S4810 switches [FTOS] to demonstrate Dell Force10′s layer 2 mulipathing technology called Virtual Link Trunking (VLT). With VLT, you can create a LAG for a server, switch, or any device that supports LACP to two different upstream switches.

Traditionally, a LAG from an access switch or server could only connect to a single upstream switch. For redundanacy purposes, many users would implement stacking on the upstream switches and then use a port-channel/LAG up to the stacked switch now seen as one logical entity. However, stacking is not the preferred solution here. Two main reasons for this is that stacking provides a single control plane mechanism that is managed by the master switch; there is no hitless failover. Compare this to VLT which provides a dual control plane mechanism and is hitless in nature. Additionally, when upgrading the switch firmware, the entire stack would need to be brought down. With VLT, one switch can be upgraded at a time without bringing down the other switch.

Stacking is more seen at the ToR or access layer. The ToR switches are usually stacked and VLT is then used upstream to the aggregate and core switches. However, if the ToR switch supports VLT such as the S4810 does, VLT can also be used from the switch down to the server. 1 GbE switches like the Dell S50N and Dell S60 do not support VLT, so, in these cases, stacking can still be employed.

In the least recommended approach, if no VLT or stacking is used at the aggregate layer connecting to the ToR on a layer 2 network, spanning tree protocol (STP) would need to be employed to block redundant links. This would create link and switch level redundancy. The issue with this is that you lose half the ports/bandwidth on the switch. By leveraging VLT, you can have an active-active multi-path connection from an access server/switch to two upstream switches seen as one logical entity employing a dual control plane mechanism. No putting-up with STP or blocked ports! (more…)