The lack of usable storage capacity is one of the constant walls IT professionals beat their head against. This is especially interesting since one of the primary focal points of any storage project is expansion capability. We always want to have a growth path should our organization experience planned (or unplanned) data growth. Nobody wants to resort to storage silos or deleting existing data just to make room for new data. So why is it that expansion is such a headache when we seemingly plan for it from the beginning?
Horizontal Expansion Can Be Pricey
A quick description of horizontal expansion: the process of adding more storage capacity by adding an additional SAN and connecting it through the network to the original SAN/s. Even though we may plan for expansion, the sticker shock of a new SAN can still be a lot to overcome. And if additional capacity is the only necessity, the value is hard to justify. Now if additional performance, CPU, and controllers are also needed, then horizontal expansion could likely be the best bet. If additional redundancy is desired, then horizontal expansion is certainly an attractive proposition as replication can be set up between the two SANs. Again, if capacity is the primary requirement then purchasing another SAN is likely not the most cost effective method of expansion.
Partial Population Delivers Less Performance
A quick description of partial population: limiting the number of drives in an initial SAN purchase with the anticipation of adding the missing drives later as a method of expanding the storage pool. Partially populating a SAN can be a good option for a lot of organizations as it helps keep the cost of the initial SAN purchase low and also provides the cheapest method of expansion. In a partially populated system, when additional capacity is needed, an IT professional simply adds drives to the empty slots. There are a few things to keep in mind with partial population. First, limiting the number of drives initially not only minimizes usable capacity, it also minimizes performance because there are not as many drives/SSDs which boost performance. The lack of performance can put an enormous drag on the network. This can be particularly tricky to explain if the SAN purchased is an All-Flash array with a partially populated shelf, as these are often purchased for their extremely high performance capabilities. Secondly, once the shelf has been fully populated, there is nowhere to expand and we’re back to square one.
Expansion to the Cloud: Good Idea or No?
Some SAN vendors offer a “Tier to the Cloud” expansion capability, where all infrequently accessed data is tiered to the cloud. This can be a good option, although it can be very pricey. Sending data to the cloud is typically relatively inexpensive; however, retrieving data is the more expensive endeavor. A good understanding of the costs associated with the cloud is necessary here since each cloud vendor has their own cost structure.
Vertical Expansion for the Win!
A quick description of vertical expansion: the method of increasing storage capacity by adding a JBOD (Just a bunch of Disks) to an existing storage array. A JBOD does not have CPU or memory and is typically very inexpensive compared to the SAN. This is perhaps the simplest form of expansion as it typically involves adding a shelf of disks into the rack and connecting it to the SAN via SAS connectivity. This instantly boosts the amount of capacity available for storing data and also increases performance. There is no additional CPU or memory, so be cognizant of this. This method is cost effective, simple and easy to implement.