In some previous posts, I highlighted how VVols introduces the concept of “undo” format snapshots where the VM is always running on the base disk. I also mentioned that this has a direct impact on the way that we do snapshots on VMs that support VSS, the Microsoft Volume Shadow Copy Service. But before getting into the detail regarding how VVols is different, it’s worth spending some time understanding whats going on when VSS is called to quiesce applications when a traditional snapshot is taken. If you try to research this yourself, you’ll find that there is very little information…
There is a subtle difference in maintenance mode behaviours between VSAN version 5.5 and VSAN version 6.0. In Virtual SAN version 5.5, when a host is placed into maintenance mode with the “Ensure Accessibility” option, the host is maintenance mode continues to contribute its storage towards the VSAN datastore. In other words, any VMs that had components stored on this host still remained fully compliance with all of the components available. In VSAN 6.0, this behaviour changed. Now, when a host is placed into maintenance mode, it no longer contributes storage to the VSAN datastore, and any components that reside…
There is a new snapshot format introduced in VSAN 6.0 called vsanSparse. These replace the traditional vmfsSparse format (redo logs). The vmfsSparse format was used when snapshots of VMs were taken in VSAN 5.5, and are also the format used when a snapshot is taken of a VM residing on traditional VMFS and NFS. The older vmfsSparse format left a lot to be desired when it came to performance and scalability. This KB article from our support team, indicating that no snapshot should be used for more than 72 hours, and snapshot chains should contain no more than 2-3 snapshots,…
In Virtual SAN version 6.0, VMware introduced support for an all-flash VSAN. In other words, both the caching layer and the capacity layer could be made up of flash-based devices such as SSDs. However, the mechanism for marking some flash devices as being designated for the capacity layer, while leaving other flash devices as designated for the caching layer, is not at all intuitive at first glance. For that reason, I’ve included some steps here on how to do it.
Well, I got so many questions about my previous articles on a new way of doing snapshots with VVols that I decided to take the time and get even deeper into their behaviour. In this setup, I take a Windows 2008 Guest OS running in a virtual machine deployed on an NFS datastore, and I compare it to an identical VM deployed on a VVol datastore. This is purely from looking at how we do snapshots. Remember with VVols, snapshots always run on the base disk, compared to the traditional way of doing snapshots where the VM always run on the…
One of the most common issues I got questions about in VSAN 5.5 was “why is VSAN deploying thick disks, when all of the documentation stated that VSAN deploys thin disks”? The answer was quite straight forward, and was due to the fact that the VMs were being deployed without a VM Storage Policy. This meant that it went through the standard VM deployment wizard which offered administrators the option of thin, lazy-zeroed thick (LZT) and eager-zeroed thick (EZT). The default option is LZT, which if you just do click-click-click (just like I do) when deploying a VM, then you…
I was heavily involved in the documentation effort for VSAN 6.0, but I know that not everyone likes to RTFM, so to speak. What I thought I would do in this post is give an overview of the upgrade process, and highlight some considerations. But I really would urge you to read through the VSAN 6.0 Administrators Guide, and perhaps the VSAN Troubleshooting Reference Manual, especially the sections dealing with upgrades, if you do plan to upgrade from VSAN 5.5 to 6.0. There is a lot of useful information there. There are four steps to the upgrade process: Upgrading vCenter…