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 part two of what is now 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 this part am going to go through the simple task of extending the cluster by adding new All Flash Disk Groups on the host I added in part one and then go through the actual Hybrid to All Flash migration steps.
The configuration of the VSAN Cluster after the upgrade will be:
- Four Host Cluster
- vCenter 6.0.0 Update 2
- ESXi 6.0.0 Update 2
- One Disk Groups Per Host
- 1x 480GB SSD Cache and 2x 1000GB SSD Capacity
- VSAN Erasure Coding Raid 5 FTT=1
- DeDuplication and Compression On
As mentioned in part one I added a new host to the cluster in order to give me some breathing room while doing the Hybrid to All Flash upgrade as we need to perform rolling maintenance on each hosts in the cluster in order to get to the All Flash configuration. Each host will be entered into maintenance mode and all data evacuated. Before the process is started on the initial three hosts lets go ahead and create a new All Flash Disk Group on the new hosts.
To create the new Disk Group head to Disk Management under the Virtual SAN section of the Manage Tab whilst the Cluster and click on the Create New Disk Group Button. As you can see below I have the option of selecting any of the flash devices claimed as being ok for VSAN.
After the disk selection is made and the disk group created, you can see below that there is now a mixed mode scenario happening where the All Flash host is participating in the VSAN Cluster and contributing to the capacity.
Upgrade Disk Group from Hybrid to All Flash:
Ok, now that there is some extra headroom the process to migrate the existing Hybrid Hosts over to All Flash can begin. Essentially what the process involves is placing the hosts in maintenance mode with a full data migration, deleting any existing Hybrid disk groups, removing the spinning disk, replacing them with flash and then finally creating new All Flash disk groups.
If you are not already aware about maintenance mode with VSAN then it’s worth reading over this VMware Blog Post to ensure you understand that using the VI Client is a big no no. In this case I wanted to do a full data migration which moves all VSAN components onto remaining hosts active in the cluster.
You can track this process by looking at the Resyncing Components section of the Virtual SAN Monitor Tab to see which objects are being copied to other hosts.
As you can see the new host is actively participating in the Hybrid mixed mode cluster now and taking objects.
Once the copy evacuation has completed we can now delete the existing disk groups on the host by highlights the disk group and clicking on the Remove Disk Group button. A warning appears telling us that data will be deleted and also lets us know how much data is currently on the disks. The previous step has ensured that there should be no data on the disk group and it should be safe to (still) select Full data migration and remove the disk group.
Do this for all existing Hybrid disk groups and once all disk groups have been deleted from the host you are ready to remove the existing spinning disks and replace them with flash disks. The only thing to ensure before attempting to claim the new SSDs is that they don’t have any previous partitions on them…if so you can use the ESXi Embedded Host Client to remove any existing partitions.
Warning: Again it’s worth mentioning that any full data data migration is going to take a fair amount of time depending on the consumed storage of your disk groups and the types of disks being used.
Repeat this process on all remaining hosts in the cluster with Hybrid disk groups until you have a full All Flash cluster as shown above. From here we are now able to take advantage of erasure coding, DeDuplication and compression…I will finish that off in part three of this series.