Yellow Bricks

by Duncan Epping

Howto

New whitepapers

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VMware recently posted two new Whitepapers, which are most definitely worth reading:

VMware VMFS Volume Management
Technical explanation as to how VMFS Volume Manager handles disks that are presented to the ESX server. This informational note covers use settings to mount or resignature volumes that appear as duplicates to the original volumes created by VMFS.

SQL Server and VMware Virtual Infrastructure
Microsoft SQL Server is a very popular and widely deployed general purpose database server supported on Windows Sever operating systems. As customers embrace a “virtualize first” policy for all applications within their enterprises, they often need guidelines for deploying SQL Server in VMware Infrastructure. This paper should help you understand how to characterize your SQL Server databases for virtualization and the best practices for designing VMware Infrastructure to support SQL Server.

Resizing your VMFS the right way, exploring the next version of ESX/vCenter

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I’ve been playing around with my vSphere/Next gen ESX lab. I was replaying the VMworld lab and one of the assignments was to  resize a VMFS volume. Yes that’s correct, resize not extent. Extents have been discussed by many and the general consensus is avoid them if/when possible. But when running out of diskspace you don’t always have the option to avoid them. Some can’t afford the downtime that comes with a “cold migration”, and most aren’t willing to take the risk of using storage vmotion when running out of diskspace. (Snapshot is placed on source VMFS volume) This has all been solved in the next version of ESX/vCenter. You can resize your VMFS volume without resorting to extents, and you can do this with the vCenter client.

The original size:

First thing you will need to do is increase the size of the LUN on your SAN. If your SAN doesn’t support LUN resizing you can still do it the old fashion way, extent. [Read more…] about Resizing your VMFS the right way, exploring the next version of ESX/vCenter

Speed up your powershell scripts

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On the VI Toolkit blog there’s a great article for people like me. They explain how to speed up your scripts. I’m no powershell guru, and these kind of articles are more than welcome to boost my scripting skills.

In short, it comes down to these three tips:

  1. Try to load as many objects as possible into arrays beforehand. Once you’ve got them loaded you can use them as arguments to multiple calls without having to resort to potentially expensive lookups every time.
  2. Just like in sample 1 above, when you’ve loaded objects, use the objects directly rather than using their names. This is usually not hard as our cmdlets are designed to take object first-and-foremost, and names are supported just as a convenience.
  3. If you absolutely need to load a single VM object by name, load it using the Get-VMFast function below. While this approach can certainly help, it’s not nearly as good as using the other two techniques mentioned above.

Head over to the VI Toolkit blog and start reading.

Disabling the VMFS-2 module! Exploring the next generation of ESX

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When I started out with ESX 3.0.x the first thing I wanted to do was disable the VMFS-2 driver. There’s no need for it when you’re not accessing VMFS-2 volumes and removing it can lead to performance gains or at least a faster rescan of your storage. Removing it, according to to this section of the VMware website, was supposed to be really easy:

vmkload_mod -u vmfs2

Unfortunately, this just unloads the module and every time the server gets rebooted the module is loaded again. Same goes for the esxcfg-module command, it unloaded it but after a reboot the module was loaded again. You could add the command to /etc/rc.local of course. This would unload the module every time the server booted. I’m not a big fan of manually changing files like this, and luckily as of the next generation of ESX(vSphere) this doesn’t seem to be necessary anymore:

esxcfg-module -d
-d|--disable - Disable a given module,
indicating it should not be loaded on boot.

The funny thing is when I run the “esxcfg-module -l” command it still lists the module as loaded. If I run the “esxcfg-module -q”, which only queries the enabled modules, it’s not listed. After a closer investigation I noticed that the following line changed in “/etc/vmware/esx.conf”:

/vmkernel/module/vmfs2/enabled = "false"

I did a cross-check, it’s most definitely not loaded. Cool, remember this one “esxcfg-module -d”. It will come in handy some day.

VMFS recognized as a snapshot what to do? Exploring the next version of ESX…

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Your VMFS has been recognized as a snapshot, what are you going to do? Hopefully most of you have read my previous post on this topic by now. If you didn’t, be very ashamed and start reading my EnableResignature post before you continue.

I was just playing with a VMworld Europe lab manual, which was about the next version of ESX/vCenter(Part of vSphere). I noticed the following new command on the command-line: esxcfg-volume. I did a help and the following showed up:

-l | --list
-m | --mount <vmfs uuid|label>
-u | -- umount <vmfs uuid|label>
-r | -- resignature <vmfs uuid|label>
-M | --persistent-mount <vmfs uuid|label>

As you can imagine this command will come in handy when a VMFS/LUN is being recognized as a clone or snapshot! With version 3.5 you needed to change an advanced setting. This setting wasn’t specifically for just one LUN, but for all of them, which is a risk. With the next version of ESX you could do the following if a volume has been detected as a snapshot and you want to resignature it:

  1. esxcfg-volume -l
  2. esxcfg-volume -r 49ba276a-c9e135b6-26f8-000c29123ede

Or if the current cloned volume isn’t connected you could also just mount it:

  1. esxcfg-volume -l
  2. esxcfg-volume -m 49ba276a-c9e135b6-26f8-000c29123ede

And if you are absolutely sure the cloned volume will not return you could mount it persistantly, which is the equivallent of “EnableResignature=0, DisallowSnapshotLUN=0”:

  1. esxcfg-volume -l
  2. esxcfg-volume -M 49ba276a-c9e135b6-26f8-000c29123ede

Don’t you just love this new exciting command-line magic! There’s more to come over the next days/weeks.

btw: there’s also a way of doing this from the GUI… Just add a new LUN, select the LUN that you want to mount, depending on what needs to be done pick “Assign a new signature” or “Keep Existing Signature”. But where’s the fun in that?