When VSAN 6.2 was released earlier this year it came with new and enhanced features and with the price of SSDs continuing to fall and an expanding HCL it seems like All Flash instances are becoming more the norm and for those that have already deployed VSAN in a Hybrid configuration the temptation to upgrade to All Flash is certainly there. Duncan Epping has previously blogged the overview of migrating from Hybrid to All Flash so I wanted to expand on that post and go through the process in a little more detail. This is the final part of a three part blog series with the process overview outlined below.
Use the links below to page jump.
- Upgrade Existing Hosts to 6.0 Update 2
- Expanding VSAN Cluster
- Upgrade License
- Upgrade Disk Format
- Upgrade Disk Group from Hybrid to All Flash
- Create new Policy and Migrate VMs
- Enable DeDupe and Compression
In part one I covered upgrading existing hosts, expanding an existing VSAN cluster and upgrading the license and disk format. In part two I covered the actual Hybrid to All Flash migration steps and in this last part I will finish off by going through the process of creating a new VSAN Policy, migrate existing VMs to the new policy and then enable deduplication and compression.
Before continuing it’s worth pointing out that after the Hybrid to All Flash migration you are going to be left with an unbalanced VSAN cluster as the full data evacuation off the last Hybrid host will leave that host without objects. Any new objects created will work to re-balance the cluster however if you want to initiate a proactive re-balance you can tit the re-balance button from the Health status window. For more on this process check out this post from Cormac Hogan.
Create new Policy and Migrate VMs:
To take advantage of the new erasure coding now in the VSAN 6.2 All Flash cluster we will need to create a new storage policy and apply that policy to any existing VMs. In my case all VMs where on the Default VSAN Policy with FTT=1. The example below shows the creation of a new Storage Policy that uses RAID5 erasure coding with FTT=1. If you remember from previous posts the reason for expanding the cluster to four hosts was to cater for this specific policy.
To create the new Storage Policy head to VM Storage Policies from the Home page of the Web Client and click on Create New VM Storage Policy. Give policy a name, click Next and construct Rule-Set 1 which is based on VSAN. Select the Failure tolerance method and choose RAID-5/6 (Erasure Coding) – Capacity.
In this case with FTT=1 chosen RAID5 will be used. Clicking on Next should show that the existing VSAN datastore is compatible with the policy. With that done we can migrate existing VMs off the Default VSAN Policy onto the newly created one.
To get an list of what VMs are going to be migrated have a look at the PowerCLI commands below to get the VMs on the VSAN Datastore and then get their Storage Policy. The last command below gets a list of existing policies.
To apply the new Erasure Coding Storage Policy its handy to get the full name of the policy.
To migrate the VMs to the new policy you can either do it one by one via the Web Client of do it on mass via the following PowerCLI script.
$VMs = Get-Datastore VSAN-000 | get-vm
$StoragePolicy = "VSAN AF Erasure Coding"
foreach ($VM in $VMs)
Get-VM -Name $VM | Set-SpbmEntityConfiguration -StoragePolicy $StoragePolicy
Once run the VMs will have the new policy applied and VSAN will work in the background to get those VM objects compliant. You can see the status of Virtual Disk Placement in the Virtual SAN tab of the Monitor Tab of the cluster.
Enable DeDupe and Compression:
Before I go into the details…for a brilliant overview and explanation of DeDupe and Compression with VSAN 6.2 head to this post from Cormac Hogan. To enable this feature we need to double check that the licensing is correct as detailed in the first post and also ensure that all previous steps relating to the Hybrid to All Flah migration has taken place. To turn on this feature head to the General window under the Virtual SAN Settings menu on the cluster Manage tab and click on the Edit button next to Virtual SAN is Turned ON.
Choose Enabled in the drop down and take note of the checkbox that talks about Allow Reduced Redundancy understanding what that means by reading the info box as shown above. Once you click on the process to enable DeDuplication and Compress will begin…this process will go through an reconfigure all Disk Groups similar to to the process to upgrade from between Hybrid and All Flash. Again this will take some time depending on the number of host, number of disk groups and type of disks in the cluster.
Below I have shown the before and after of the Capacity window under the Virtual SAN tab in the Monitor section of the Cluster view. You can see that before enabled, there is a message saying that DeDeuplication and Compression is disabled.
And after enabling DeDuplication and Compression you start to get some statistics relating to both of them in the window relating to savings and ratios. Even in my small lab environment I started to see some benefits.
With that complete we have finished this series and have gone through all the steps in order to get to an All Flash VSAN Cluster with the newest features enabled.