About Dusan Tekeljak

Dusan has over 6 years experience in Virtualization field. Currently working as Senior VMware plarform Architect at one of the biggest retail bank in Slovakia. He has background in closely related technologies including server operating systems, networking and storage. Used to be a member of VMware Center of Excellence at IBM, co-author of several Redpapers. His main scope of work consists from designing and performance optimization of business critical virtualized solutions on vSphere, including, but not limited to Oracle WebLogic, MSSQL and others. He holds several IT industry leading certifications like VCAP-DCD, VCAP-DCA, MCITP and the others. Honored with #vExpert2015 and 2016 awards by VMware for his contribution to the community. Opinions are my own!

ESXi installation fail with IBM x3650 M4 and m5110e storage controller after Firmware upgrade

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Yesterday, we experienced a problem where we couldn’t install ESXi on the one of ours IBM x3650 M4 servers. We suspected it could be a firmware issue as we performed a complete firmware upgrades just before the installation. If you already had your ESXi installed and did the firmware upgrade … Continue reading

Bricked QLogic Broadcom BCM57840 after driver update

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Two weeks ago, we started with regular updates of our Flex system servers, including drivers and firmwares. It is good practice to update drivers first so I followed this procedure as usually. Our update list included ESXi driver for CN4022 (QLogic Broadcom BCM57840). Since IBM/Lenovo doesn’t provide VMware drivers for … Continue reading

Set up an alert for port blocked by vSwitch security policy

Today I’m gonna show you, how to be alerted when VM port is being blocked by security policy defined on portgroup or vSwitch level. If you are not aware so far, these settings prevents VM users (or attackers) to change MAC address from the operating system. There are three security … Continue reading

Enabling agentless Guest (VM) RAM monitoring with vRealize Operations 6.3+

Agentless monitoring of the Guest RAM metrics is one of the new feature introduced with vRealize Operations 6.3 with vSphere 6.0 U1. I was really happy to finally see this functionality, as memory metrics which are provided by default are not accurate and I would say almost useless when trying … Continue reading

Just Another ESXi 6.0 Storage APD Handling Bug

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It’s been a while since we experienced partial outage on our storage infrastructure running under IBM SVC storage. Few LUNs (vdisks in IBM SVC world) presented from storage went offline. I’m not going into details why it happened as HW problems just happens sometimes. Important thing is how are you … Continue reading

Broadwell ESXi 6.0 Exception 14 PSOD and Lenovo support fail

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You may already have heard about known issue with Intel Broadwell Family CPUs (Intel Xeon CPU E5-26xx v4 CPUs)  where you can hit Exception 14 PSOD if you are running older microcode. If not, you can read about it in kb2146388 From there you can clearly see you need to … Continue reading

IBM/Lenovo Networking and security issue using Easy Connect mode!

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A couple of months ago, after a migration from our legacy vSphere environment into our brand new vSphere based on IBM/Lenovo Flex Systems environment. Some of the our VMs stopped or were randomly responding on the network. My networking team discovered those VMs have duplicate MAC addressees with another VMs. … Continue reading

Fixed: Cross vCenter vMotion with shared storage bug

I’m in the middle of the project where I need to split up my environment into two vCenters so I decided to update part of it to vSphere 6.0 to ease up my work and operations tasks later on. I do have a stretched infrastructure across the datacenters including storage … Continue reading

Warning: Extending virtual disks in ESXi 6.0 can pause your VM!

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As  I’m planning to deploy ESXi 6.0 in our environment, I’m doing research for the all issues or behavioral changes coming with vSphere 6.0. I have discovered one serious change in behavior which came with ESXi 6.0 and I don’t think it was announced anywhere and it can cause outage in your … Continue reading

Security issue after updating to vCenter 6.0

I did a crazy thing last week, I decided to update our vCenter appliance (VCSA) from version 5.5U3a to version 6.0 Update1 3040890. I was surprised how flawlessly it went. It was finished in couple of hours, “almost” everything was working as expected, so big success 🙂 Until users started … Continue reading