Drobo recommends that when researching storage devices, the primary performance metric is throughput. A quick scan of web reviews reveals that a majority of the focus is on how quickly the device can read or write large files. Think drag-and-drop. While this is a great metric if your device will primarily be used for data archive and backups, one must also consider IOPS performance as it relates to as workspace storage. IOPS (Input/Output Operations Per second) performance is measured by how quickly the device can work with small bits of data.
The first sign that you might not have sufficient IOPS comes with slow response times within the application. If you’re waiting for the application to move between screens or files, the disk subsystem may be working at its maximum IOPS capacity. This not only slows the application, but also incurs significant latency.
While adding additional rotational drives to the RAID system will improve both throughput and IOPS performance, the benefits are limited by the low IOPS rating of the HDDs. Moving to an all SSD configuration vastly improves performance, but comes with a significant reduction in capacity.
All modern Drobos include support for automated Data-Aware Tiering. This technology was first introduced with the Drobo B1200i iSCSI business SAN, and is now available on all prosumer models. With the addition of an accelerator bay to the bottom of the device, it allows the Drobo to take advantage of the high IOPS performance of a SSD, while still offering the expansive storage space of a HDD. The Drobo uses the SSD in the accelerator bay to cache hot data, providing accelerated performance to the data you use most frequently. With the addition of the mSATA SSD, the IOPS performance of the Drobo is three times what is possible in a five drive all-HDD configuration.