Yellow Bricks

by Duncan Epping

Various

Reminder: Free Kindle copy of vSphere 5 and 4.1 Clustering Deepdive

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Just a reminder, if you want your free Kindle copy of the vSphere 5.0 Clustering Deepdive or the vSphere 4.1 HA and DRS Deepdive, make sure to check Amazon (US Kindle Store) today and tomorrow (Wednesday June the 5th and Thursday June the 6th)! You can download the Kindle copy of both these books for free, yes that is correct ZERO dollars.

So make sure you pick it up either before the promo expires…

** Note I have linked the US Kindle stores, it is also available for free in local Kindle stores, just do search! **

 

Train Signal free trial for new subscription model

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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?

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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?

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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.

DRS not taking CPU Ready Time in to account? Need your help!

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For years these rumors have been floating around that DRS does not take CPU Ready Time (%RDY) in to account when it comes load balancing the virtual infrastructure. Fact is that %RDY has always been a part of the DRS algorithm but not as a first class citizen but as part of CPU Demand, which is a combination of various metrics but includes %RDY. Still, one might ask why %RDY is not a first class citizen.

There is a good reason though that %RDY isn’t, just think about what DRS is and does and how it actually goes about balancing out the environment, trying to please all virtual machines. Yes a lot of possibilities indeed to move virtual machines around in a cluster. So you can imagine that it is is really complex (and expensive) to calculate what the possible impact is after a virtual machine has been migrated “from a host” or “to a host” for all of the first class citizen metrics.

Now, for a long time the DRS engineering team has been looking for situations in the field where a cluster is balanced according to DRS but there are still virtual machines experiencing performance problems due to high %RDY. The DRS team really wants to fix this problem or bust the myth – what they need is hard data. In other words, vc-support bundles from vCenter and vm-support bundles from all hosts with high ready times. So far, no one has been able to provide these logs / cold hard facts.

If you see this scenario in your environment regularly please let me know. I will personally get you in touch with our DRS engineering team and they will look at your environment and try to solve this problem once and for all. We need YOU!