One of the trickiest calculations IT managers are called upon to make, when it comes to data storage options, is the price of All-Flash Arrays (AFAs) compared to the price of HDD.
As George Crump, president of Storage Switzerland, noted in a recent column, “the raw price per gigabyte of flash is declining rapidly due to an increase in production and density per flash cell.”
But he quickly notes that that per gigabyte price drop is often offset by the reality that flash can be less durable than HDD. Conversely, he adds, “an AFA largely mitigates the impact of faster wear out. Most AFAs have redundant components, so if a NAND wears out there are other NANDs available to take its place. The majority of all-flash array vendors overprovision the drives, so they may only present 75% of the capacity of the drive to the storage system. Overprovisioning allows fewer writes across more NAND cells. While sacrificing some capacity, it does extend the apparent life of the drive.”
In other words, it’s complicated.
Crump walks through the myriad ways flash pricing can get a little “fuzzy,” largely due to what’s known as “data efficiency” considerations, then lays out three potential approaches for IT managers to use. Either “take a very conservative approach and buy with the assumption that there will be no gains in capacity from data efficiency,” assume a 2.5 times data efficiency gain, or push for a data efficiency guarantee that many vendors are now providing.
In Crump’s view, flash pricing isn’t quite an exact science, which leaves IT managers with the task of understanding all the possible options then driving for the best bargain.