Netapp is one of the most popular storage arrays on the market. Many customers buy this array because it supports both block and file (unstructured) data, which is its strength. It provides several features that are important to storing and managing your file data. These include compression, deduplication, native NFS, and SMB support as well as scale-out cluster environments, which allows for clusters to add nodes and more storage to each node.
Another of these features is the desired space guarantee when defining a NetApp volume. The choices are none, volume, and file. The setting that the administrators choose can have a dramatic effect on the reported aggregate free space on an array. An example is the best to explain the differences in these settings.
As an example, if we are defining a volume that is 4 GB and we use the “guarantee=none” option means that after the system creates the volume, it reports 0 GB as used. However, if you changed your guarantee to guarantee=volume, now this volume indicates 4 GB used (it appears as a thick provisioned volume, even though the volume is empty. The system reserves 4GB for the volume, and none of its free space in the system aggregate.
It is easy to jump to the conclusion that one of these settings is always right. The reality is there are times and places for both options. Guaranteeing your disk capacity is secured for a volume available has the benefit of making sure critical applications don’t unexpectedly run out of storage space, which could have disastrous consequences. One of the other reasons to use volume guarantees is to avoid “runaway file growth”. If you are using NetApp as a file storage device and you want to make sure a specific set of users can only use a predetermined amount of space, a volume guarantee of volume, is a perfect option for this type of use case.
Using the “guarantee = none” is the best way to optimize storage usage when you are unsure of how much space users and applications need. Storage environment’s users often insist on more capacity than they need “just in case.” When a whole collection of users apply the same logic, an organization may have dozens of terabytes of capacity that looks like it is in use but is free space.
VSI recently worked with a customer with 15PBs of NetApp storage. When they initially install their NetApp systems, they started with the “guarantee = volume” setting as their default configuration. Initially, this seemed logical, but two years into an infrastructure refresh project, they were out of space. The organization’s IT team met with NetApp to ask them why they didn’t account for their capacity needs correctly, even though they were buying 50% more storage than their projected demand. There was no clear answer because the project was two years underway before the review.
Both NetApp and the customer were at a standstill. NetApp was, of course, happy to sell the customer more storage. The customer thought it had no other choice. The customer, though, is a VSI customer. When we showed them how to turn on one feature within our solution, the situation changed for the better. That feature is called “volume locked free space.”
Showing this information revealed a stunning result – they had 3 PB of volume locked free space. This open space was hard-set to specific volumes but not in use and not available to other volumes that could use it. The 3PBs was 20% of their overall storage space.
Another challenge in finding this free space is the 3PB was the cumulative free space from all their NetApp volumes. It wasn’t until the used VSI to show the aggregate free space that the problem became apparent. The customer is using VSI to list all volumes across all arrays. They can then use VSI to see what volumes have the most available capacity. Then they can change the volume guarantee from volume to none with a click of a mouse so that users and applications can access the data.
After doing a detailed analysis using VSI, the customer realized about 2 of the 3 PB of volumes could and should be using “guarantee = none” setting. The customer made these changes online, suffering no downtime, no change control, and instant space availability.
So how can you reduce your Netapp bill? By buying what you need and making sure you are making the best choices to get the most capacity out of your storage purchases. Not sure you have the resources to do so? Contact us below.