Express Bay is an externally accessible storage slot that is designed to accept a high-performance PCI Express (PCIe) solid-state drive (SSD), Serial-attached SCSI (SAS)- or Serial ATA (SATA)-based SSD, or hard disk drive (HDD).
The Express Bay supports four dedicated lanes of bandwidth, up to 25 watts of power to PCIe SSDs in a 2.5-inch or 3.5-inch disk drive form factor, as well as two additional lanes for HDDs and SSDs based on SAS, SATA and, in the future, may be based on SATA Express. The Express Bay is designed to accommodate PCIe SSDs that use proprietary protocols as well as those based on standards such as Non-Volatile Memory Express (NVMe) and SCSI Express (SCSIe).
In a typical configuration, one or more Express Bays are located in a server along with standard drive bays that accept SAS- or SATA-based SSDs or HDDs.
A group of technology vendors created Express Bay to overcome constraints associated with standard disk drive bays that were originally designed for HDDs, not for faster SSDs. Standard disk drive bays are typically limited to 9 watts of power, and one or two lanes of bandwidth.
In addition, the industry group created Express Bay to provide more flexible management options for PCIe SSDs. The SSDs located in PCIe slots within servers typically cannot be accessed without shutting down the system and opening the server hardware box. The Express Bay would permit externally serviceable PCIe SSDs that can be plugged into a running server.
Original equipment manufacturers (OEMs) have the option to choose the number of Express Bays they will support and the power level they will allot to each Express Bay in a server.