ONTAP FlexGroup volumes offer incredible performance and massive capacity scalability. What if you have data today in a Flexible volume (FlexVol) but decide you want a FlexGroup volume? How best do you go about this change?
First, we should confirm that you should in fact consider the change. Starting with ONTAP 9.12.1, the maximum FlexVol size tripled from 100TB to 300TB. If your workload is well under 300TB, and you don’t expect it to grow to that level, a FlexVol might be the best place to stay. Every version of ONTAP delivers better single volume performance so simply upgrading to a more current version of ONTAP might be the best course of action.
However, what if you decide you do need to convert to a FlexGroup volume? What is the best process? Next, we need to determine the reason for the move as that will best determine the path forward.
Need greater capacity
Let’s say you have a large pool of cool data. The performance of a FlexVol is sufficient, but you need to grow that pool of data well beyond 300TB. In this case you could perform an in-place FlexVol to FlexGroup volume conversion.
An in-place conversion leaves all existing data in the original volume but expands the data container by adding additional member volumes creating a FlexGroup volume. It will not accelerate any of the original data but does allow for seamless expansion to multiple PB capacity with new data being optimally placed across the new member volumes.
It is important to note that after doing the conversion, you will have one member volume (the original volume) that is quite full and other volumes that are empty. This is normal and will eventually equalize over time.
Need greater performance
What if instead of needing greater capacity, you have a workload that now demands much greater performance. Perhaps it is exceeding what as single storage node can satisfy. In this case, a different approach is recommended.
For these cases, a new separate FlexGroup volume should be created with an optimal number of member volumes. ONTAP does this automatically, and this number will vary based on how large your data set is and the composition of your ONTAP cluster. Data in the original FlexVol should be copied to the new FlexGroup volume.
This is most easily done by mounting the new FlexGroup volume as a different mount point then copying the data using NetApp’s free XCP software. XCP can copy significant amounts of data and the new FlexGroup volume will place the data in an optimal layout across the member volumes.
A short cut over is required, after which the clients using the original FlexVol should unmount it, XCP can do a final copy pass, and then the FlexVol can be placed offline. The new FlexGroup can then be mounted to replace the FlexVol and the clients can remount the share.
Although more work, this leaves you with an optimally laid out FlexGroup volume, ready to deliver a huge increase in throughput and the ability to grow as needed.
There you go, if you need to move from a FlexVolume to a FlexGroup, you have 2 options depending on your needs and situation.
