Yellow Bricks

by Duncan Epping

esxi

VMware Communities Roundtable podcast tonight!

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I’m really looking forward to the podcast tonight. We’ve got Chad Sakac from EMC joining in to elaborate on topics like:

  • What VMware, EMC and Cisco are doing together around the Next Generation Datacenter
  • What’s coming in vStorage
  • Reference Architectures for Tier 1 applications like Exchange, SQL Server, Sharepoint
  • What we’re seeing around Disaster Recovery for VMware
Most of you probably discovered Chad’s blog by now, if you didn’t check it out. Especially his post on vStorage gives you an idea what Chad and his team are working on. But also the more technical posts like this one on VMFS Resignaturing contain really valuable info.
Anyway join us on the podcast. Wednesdays noon PST / 3pm EST / 8pm GMT. You can find live Connect info here. (For those like me having trouble converting time to your time zone click here.)

NFS.LockDisable what should it be 1 or 0

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There has been a lot of discussion(check Scott’s take on this) around this advanced NFS setting called “NFS.LockDisable”. In short, you can disable the locking mechanism on NFS volumes with this setting.

In the past NetApp had a best practices document which stated that it should be disabled by setting it to “1”. But, as some noticed this can and probably will result in corrupt file-systems. So this “best practice” mysteriously disappeared from the NetApp VI3 Best Practices guide and a KB Article with the VMware best practice on this setting popped up.

So if you did set “NFS.LockDisable” to 1 please change it back to “0”.  

It might be beneficial to also implement the “prefvmx.ConsolidateDeleteNFSLocks” that Scott discussed along with patch ESX350-200808401-BG. This setting is to avoid long delays when deleting ESX snapshots. This can take up to 30 seconds, which is quite long compared to iSCSI or FC. So you should only implement this fix if you run NFS and do VMware snapshots at them same time and are experiencing these dalays.

I do recommend that everyone with an NFS filer takes a look at the NetApp best practices document because it does contain valuable information, but before you apply it besure that it doesn’t conflict with a VMware best practice!

VCB and independent disks

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Most of you probably knew that it is impossible to snapshot an independent/persistent disk. And if you didn’t, in short: a disk that is in “independent/persistent” mode can’t be snapshot because it needs to write it’s changes immediately to the virtual harddisk. When using a snapshot(nonpersistent) writes go to a delta file.

So as I said in this article, using this mode on a specific disk is a nice way to get the full image VM without for instance that gigantic data disk. But some of you might need the snapshot functionality, and it’s not possible to change the disk state from the VirtualCenter client when the VM is up and running.

But it is possible to change the state via the command-line when the VM is running. So if you want to change the state in a VCB script for a specific disk, or want to change the state for a VM without shutting it down here you go:

Find out what the current mode is from the command line:

vmware-cmd <path to vmx file.vmx> getconfig scsi0:0.mode

Set the new mode from the command line:

vmware-cmd <path to vmx file.vmx> setconfig scsi0:0.mode “persistent”

Keep in mind that this is, as far as I know, not supported and should be tested thoroughly before using. I would prefer doing it manually and keeping it that way. Or you could always use the script that I blogged about a while back, it makes it possible to dump specific disks without having to resort to unsupported methods.

By the way, with the setconfig option you can set most vmx options!

 

Which VM is connected to an RDM?

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A friend of mine asked me if there was a way to find out which VM’s were connected to a certain RDM disk. I’ve been looking all over but couldn’t find a simple command to do this. So I ended up on the forums and found a powershell script which creates a list with all the necessary info one would like to have:

$report = @()
$vms = Get-VM | Get-View
foreach($vm in $vms){
foreach($dev in $vm.Config.Hardware.Device){
if(($dev.gettype()).Name -eq “VirtualDisk”){
if(($dev.Backing.CompatibilityMode -eq “physicalMode”) -or
($dev.Backing.CompatibilityMode -eq “virtualMode”)){
$row = “” | select VMName, HDDeviceName, HDFileName, HDMode
$row.VMName = $vm.Name
$row.HDDeviceName = $dev.Backing.DeviceName
$row.HDFileName = $dev.Backing.FileName
$row.HDMode = $dev.Backing.CompatibilityMode
$report += $row
}
}
}
}
$report

All credits for this great script go to LucD!

Defraging a VMDK

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Team Fusion wrote a great post on “defragging” vm’s and why you shouldn’t do it. Or at least be very careful about it. Make sure to read it!

Before we begin, it’s important to note that defragmentation isn’t a necessary task – your virtual machine will still work just fine even if you never defrag, and the effects of fragmentation are usually not noticeable. Personally, I’ve never feel the need to defrag. However, if for some reason you do feel the need to defrag, here’s how to do it. Note that snapshots get in the way of proper defragmenting.