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!

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

IBM FlashSystem V9000 and VMware vSphere ESXi Guidelines

I’m really glad I had opportunity to participate on a RedBook residency regarding IBM FlashSystem V9000 and VMware “Best Practices” (it was actually one of my last thing which I did as IBMer) and till the RedPaper is released for public I decided to write a sneak peek with some … Continue reading

A new IBM SVC, Storwize (Spectrum Virtualize) v7.5 brings VVols, HyperSwap…

IBM made an announcement last week that a new IBM Spectrum Virtualize Software V7.5.0 is coming soon (5th June 2015), which will bring supports for the features like vSphere VVols, HyperSwap, Microsoft ODX… If you haven’t heard yet, IBM replaced Storwize family naming earlier this year with Spectrum Virtualize Software. … Continue reading

ALERT: VENOM Vulnerability CVE-2015-3456, Clouds Exposed!

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Crowdstrike disclosed a serious VM Escape vulnerability – codename VENOM, CVE-2015-3456 which has been around here since 2004. This one is especially serious because it is affecting the VMs in their default configuration and could be also affecting thousands of the VMs in cloud. This vulnerability may allow an attacker … Continue reading