Evaluating SSDs in Virtualized Datacenters by Irfan Ahmad

Flash-based solid-state disks (SSDs) offer impressive performance capabilities and are all the rage these days. Rightly so? Let’s find out how you can assess the performance benefit of SSDs in your own datacenter before purchasing anything and without expensive, time-consuming and usually inaccurate proofs-of-concept.

** Please note that this article is written by Irfan Ahmad, follow him on twitter and make sure to attend his webinar on the 5th of June on this topic, and vote for CloudPhysics  in the big data startup top 10. **

I was fortunate enough to have started the very first project at VMware that optimized ESX to take advantage of Flash and SSDs. Swap to Host Cache (aka Swap-to-SSD) shipped in vSphere 5. For those customers wanting to manage their DRAM spend, this feature can be a huge cost saving. It also continues to serve as a differentiator for vSphere against competitors.

Swap-to-SSD has the distinction of being the first VMware project to fully utilize the capabilities of Flash but it is certainly not the only one. Since then, every established storage vendor has entered this area, not to mention a dozen awesome startups. Some have solutions that apply broadly to all compute infrastructures, yet others have products that are specifically designed to address the hypervisor platform.

The performance capabilities of the Flash are indeed impressive. But they can cost a pretty penny. Marketing machines are in full force trying to convince you that you need a shiny hardware or software solution. An important question remains: can the actual benefit keep up with the hype? The results are mixed and worth reading through.

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Train Signal free trial for new subscription model

Recently Train Signal changed the way they deliver training… Instead of buying a single training every time they changed to a subscription based model. It makes a lot of sense if you ask me. I always liked the Train Signal concept as it allows you to do a training when you have the time, instead of the standard 9 to 5 times. Especially when you need to quickly brush up in a certain area it is nice to sit down and just go over it quickly. It is $ 49,- a month, so even if you just want to do that one training by Scott Lowe on how to design a virtual infrastructure, or get to know everything about UCS from Jason Nash you could just sign up and follow that training and cancel the subscription afterwards! There is a long list of courses, if you are not interested in VMware training but rather Microsoft or Linux… don’t worry.

If you were awarded with the vExpert status this year and hadn’t seen it on twitter yet, you can sign up for a year long free training. If you are not a vExpert but would love to have a taste of this subscription based training model, sign up for a 3 day Free Trial today and just try it out!

Manual vMotion and using DRS to select a host results in no migration?

I had a question from a customer last week. He was doing a manual migration on a cluster which had DRS enabled. He was using the vSphere Web Client and was wondering if he should tick the “Allow host selection within this cluster” tickbox or not, as shown in the screen shot below. The customer decided not to tick the “host selection” tickbox and decided that DRS would pick the right destination for the virtual machine. After he clicked “Finish” he noticed that the “relocation” literally finished in seconds and he wondered if anything happened at all… When he looked at the virtual machine he noticed it was still located on the same host, how can that be?

Well the answer is fairly straight forward, in this case the DRS cluster was balanced and that is the typical situation for most clusters out there I would say. When initiating the vMotion workflow the Cluster was selected as a destination so DRS had to figure out what the best destination would be. Considering the cluster was in balance, there would be absolutely no point in moving this virtual machine so what did DRS decide? Indeed, destination = source.

If you are going through this workflow using the Web Client, make sure to tick “Allow host selection within this cluster” and select a destination other than your source… otherwise the effort was pointless.

Manual vMotion

Free Kindle copy of vSphere 5.0 Clustering Deepdive?

Do you want a free Kindle copy of the vSphere 5.0 Clustering Deepdive or the vSphere 4.1 HA and DRS Deepdive? Well make sure to check Amazon next week! I just put both of the books up for a promotional offer… For 48 hours, Wednesday June the 5th and Thursday June the 6th, you can download the Kindle (US Kindle Store) copy of both these books for free, yes that is correct ZERO dollars.

So make sure you pick it up either Wednesday June the 5th or Thursday June the 6th, it might be the only time this year it is on promo.

Pinging from different VMkernel NICs using esxcli?

Today I had a network issue in my lab, I still don’t have a clue what the issue was but I did discover something useful. I had 3 different VMkernel’s setup and I wanted to make sure each of the three had network connection to a specific destination address. After going through the esxcli command I bumped in to the following command which I found very helpful:

esxcli network diag ping -I vmk0 -H

In this case I use VMkernel Interface “vmk0″ to ping to the address “″. If I want to use a different VMkernel Interface I just specify it, so swap “vmk0″ with “vmk1″ for instance. Useful right?!

How to change the IP Address of ESXi through the commandline

I was building out my virtualized lab and instead of re-installing ESXi over and over again I figured I would just quickly clone them. Now of course this leads to a “minor” problem as the virtualized ESXi hosts will all boot with the same IP-Address. As I don’t have DHCP to my disposal I needed to change them manually, so how do you change the IP address of ESXi through the commandline?

It is actually pretty straight forward with esxcli these days. First thing I did was listing all VMkernel NICs:

esxcli network ip interface ipv4 get

This will give you the list of all VMkernel interfaces with their details (See screenshot below). Changing the IP address is just a matter of adding some parameters:

esxcli network ip interface ipv4 set -i vmk1 -I -N -t static

In your situation you will need to replace “vmk1″ with the appropriate VMkernel NIC of course and change the IP details.

change ip address of esxi

Replaced certificates and get vSphere HA Agent unreachable?

Replaced certificates and get vSphere HA Agent unreachable? I have heard this multiple times in the last couple of weeks. I started looking in to it and it seems that in many of these scenarios the common issue was the thumbprints. The log files typically give a lot of hints that look like this:

[29904B90 verbose 'Cluster' opID=SWI-d0de06e1] [ClusterManagerImpl::IsBadIP] <ip of the ha master> is bad ip

Also note that the UI will state “vSphere HA agent unreachable” in many of these cases. Yes I know, these error messages can be improved for sure.

You can simply solve this by disconnecting and reconnecting the hosts. Yes it really is as simple as that, and you can do this without any downtime. No need to move the VMs off even, just right click the host and disconnect it. Then when the disconnect task is finished reconnect it.