When VSAN 6.2 was released earlier this year it came with new and enhanced features and depending on what version you where running you might not have been able to take advantage of them all right away. Across all versions, Software Checksum was added with Advanced and Enterprise versions getting VSANs implementation of Erasure Coding (RAID 5/6) with Deduplication and Compression available for the All Flash version and QOS IOPS Limiting available in Enterprise only.
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 a two part blog post with a lot of screen shots to compliment the process which is outlined below.
Use the links below to page jump.
Warning: Before I begin it’s worth mentioning that this is not a short process so make sure you plan this out relative to the existing size of your VSAN cluster. In talking with other people who have gone through the disk format upgrade the average rate seems to be about 10TB of consumed data per day depending on the type of disks being used. I’ll reference some posts at the end that relates to the disk upgrade process as it has been troublesome for some however also worth pointing out that the upgrade process is non disruptive for running workloads.
- Three Host Cluster
- vCenter 6.0.0 Update 2
- ESXi 6.0.0 Update 1
- Two Disk Groups Per Host
- 1x 200GB SSD and 2x 600GB HDD
- VSAN Default Policy FTT=1
Upgrade Existing Hosts to 6.0 Update 2:
At the time of writing ESXi 6.0.0 Update 2 is the latest release and the builds that contain the VSAN 6.2 codebase. From the official VMware Upgrade matrix it seems you can’t upgrade from VSAN versions older than 6.1, so if you are on 5.x or 6.0 releases you will need to take note of this VMwareKB to get to ESXI 6.0.0 Update 2. A great resource for the latest builds as well as links to upgrade from head here:
For a quick upgrade directly from the VMware online host update repository you can do the following on each host in the cluster after putting them into VSAN Maintenance Mode. Note that there are also some advanced settings that are recommended as part of the VSAN Health Checks in 6.2
esxcli network firewall ruleset set -e true -r httpClient
esxcli software profile update -p ESXi-6.0.0-20160504001-standard -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml
esxcli system settings advanced set -o /LSOM/VSANDeviceMonitoring -i 0
esxcli system settings advanced set -o /LSOM/lsomSlowDeviceUnmount -i 0
After rolling through each host in the cluster make sure that you have an updated copy of the VSAN HCL and run a health check to see where you stand. You should see a warning about the disks needing an upgrade and if any hosts didn’t have the above advanced settings applied you will have a warning about that as well.
Expanding VSAN Cluster:
As part of this upgrade I am also adding an additional host to the existing three to expand to a four host cluster. I am doing this for a couple of reasons, not withstanding the accepted design position on four host being better than three from a data availability point of view you also need a minimum of four hosts if you want to enable RAID5 erasure coding (six is required as a minimum for RAID6). The addition of the fourth host also allowed me to roll through the Hybrid to AF upgrade with a lot more headroom.
Before adding the new host to the existing cluster you need to ensure that the build is consistent with the existing hosts in terms of versioning and more importantly networking. Ensure that you have configured an VMkernel Interface for VSAN traffic and marked it as such through the Web Client. If you don’t do this prior to putting the host into the existing cluster I found that the management VMKernel interface was enabled by default for VSAN.
If you notice below this cluster is also NSX enabled, hence the events relating to Virtual NICs being added. Most importantly the host can see other hosts in the cluster and is enabled for HA.
Once in the cluster the host can be used for VM placement with data served from the existing hosts with configured disk groups over the VSAN network.
At this point I upgraded the licenses to enable the new features in VSAN 6.2. As a refresher on VSAN licensing there are three editions with the biggest change from previous versions being that to get the Deduplication and Compression, Erasure Coding and QoS features you need to be running All Flash and have an Enterprise license key.
To upgrade the license you need to head to Licensing under the Configuration section of the Manage Tab whilst the Cluster is selected. Apply the new license and you should see the following.
Upgrade Disk Format:
If you have read up around upgrading VSAN you know that there is a disk format upgrade required to get the benefits of the newer versions. Once you have upgraded both vCenter and Hosts to 6.0.0 Update 2 if you check the VSAN Health under the Monitor Tab of the Cluster you should see an failure talking about v2 disks not working with v3 disks as shown below.
You can click on the Upgrade On-Disk Format button here to kick off the process. This can also be triggered from the Disk Management section under the Virtual San menu in the Manage cluster section of the Web Client. Once triggered you will see some events trigger and an update in progress message near the version number.
Borrowing from one of Cormac Hogan’s posts on VSAN 6.2 the following explains what is happening during the disk format upgrade. Also described in the blog post is a way using the Ruby vSphere Client to monitor the progress in more detail.
There are a few sub-steps involved in the on-disk format upgrade. First, there is the realignment of all objects to a 1MB address space. Next, all vsanSparse objects (typically used by snapshots) are aligned to a 4KB boundary. This will bring all objects to version 2.5 (an interim version) and readies them for the on-disk format upgrade to V3. Finally, there is the evacuation of components from a disk groups, then the deletion of said disk group and finally the recreation of the disk group as a V3. This process is then repeated for each disk group in the cluster, until finally all disks are at V3.
As explained above the upgrade can take a significant amount of time depending on the amount of disk groups, data consumed on your VSAN datastore as well as the type of disks being used (SAS based vs SATA/NL-SAS) Once complete you should have a green tick and the On-Disk format version reporting 3.0
With that done we can move ahead to the Hybrid to All Flash conversion. For details on the look out for Part 2 of this series coming soon.
Hybrid vs All-flash VSAN, are we really getting close?
VSAN 6.2 Part 2 – RAID-5 and RAID-6 configurations
VSAN 6.2 Part 12 – VSAN 6.1 to 6.2 Upgrade Steps