JBODs are expansion hard drive enclosures that usually come with redundant power & cooling and external SAS ports that allow them to be connected to some type of system as extra capacity. JBODs can be used in many ways and come in many different sizes. RAID solutions usually have expansion ports that allow you to attach them to JBODs for extra capacity, that are controlled by the RAID controllers in the main enclosure. Software Defined Storage solutions, like ZFS or object storage are really the next generation of RAID and, usually have the server engine in it’s own server enclosure and then has the main capacities of hard drives being controlled in these expansion JBOD enclosures.
RAIDs that are used for application or virtualization acceleration may come filled with SSDs for high performance and then have the larger capacity HDDs, for the data requirement, in expansion JBODs. Today’s performance HDDs (30GB to 2TB SSDs or 7.2 to 15K RPM spinning disks) come in 2.5″ form factors while the capacity HDDs (4 to 8TB, 5000-7200 RPM near line SAS disks) come in 3.5″ form factors. 2U (1U = 1.75″ in height) expansion enclosures usually hold 12 3.5″ HDDs or 24 2.5″ HDDs, standard 3U enclosures usually hold 16 x 3.5″ HDDs, 4U enclosures usually hold between 48 – 90 HDDs. These enclosures can also be used to attach HDD capacity to PCI RAID controllers that sit inside the server. We integrate these expansion enclosures, along with the appropriate HDDs & SSDs, according to the HCL (hardware compatibility list) of whatever it’s being attached to.