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SpottedHyena Posts

Mikrotik OpenVPN Server with Linux Client

I spent quite some time trying to get the OpenVPN Server working on the Mikrotik Router with a Linux client, It caused some pain and I didnt want others to go through that. I have therefore written this guide, taking you from certificate creation all the way to VPN connectivity.

For this tutorial I will have SSH to my Mikrotik (you can use a winbox terminal), I have chosen not to use WinBox for the configuration as its easier to deploy this way.

VMware Transparent Page Sharing TPS

What is TPS?

Transparent Page Sharing (TPS) is a host process that leverage’s Virtual Machine Monitor (VMM) component of the VMkernel to scan physical host memory to identify duplicate VM memory pages. The benefits of TPS are that it allows a host to reduce memory usage so you can allow more VMs onto a host, as memory is often one of the most constrained resources on a host. TPS is basically de-duplication for RAM and works at the 4KB block level.

VMware Large Snapshot Safe Removal

One of the great virtualization and VMware features is the ability to take snapshots of a virtual machine. The snapshot feature allows an IT administrator to make a restore point of a virtual machine, with the option to make it crash consistent. This feature is particularly useful when performing upgrades or testing, as if anything goes wrong during the process, you can quickly go back to a stable point in time (when the snapshot was taken).

Dell VMware 5.5 FCoE Errors

Recently I have seen an issue after upgrading some of our Dell R6xx hosts to 5.5 U2, they started showing FCoE in the storage adapters and booting took a really long time.

I looked into this and found that the latest Dell ESXi image also includes Drivers and scripts that enable the FCoE interfaces on cards that support it.

To see if you have this problem check the below steps:

NUMA and vNUMA made simple!

What is NUMA?

Most modern CPU’s, Intel new Nehalem’s and AMD’s veteran Opteron are NUMA architectures. NUMA stands for Non-Uniform Memory Access. Each CPU get assigned its own “local” memory, CPU and memory together form a NUMA node (as shown in the diagram below).

Memory access time can differ due to the memory location relative to a processor, because a CPU can access it own memory faster than remote memory thus creating higher latency if remote memory is required.