Storage providers are whetting designers’ appetites with terabytes at the top end and silicon for a range of embedded applications. Newer interfaces like Serial Advanced Technology Attachment (SATA) are now the norm as Inetgrated Drive Electronics (IDE) quickly fade, at least on the hard-drive side. And, a move to smaller form factors is without question.
The 3.5-in. drives still dominate capacity equation, but 2.5-in. is the new target. Server redundant arrays of disks (RAIDs) are now being populated with 2.5-in. Serial Attached SCSI (SAS) and SATA drives. The 1.8-in. drives are the new portable devices of choice as laptops, mobile Internet devices (MIDs), and netbooks go on a diet. Flash memory is playing a significant role in this space.
Flash Disks Everywhere
Flash is also changing the sockets for storage devices. SiliconSystems SiliconDrive II plugs into the Small Form Factor SIG MiniBlade, providing a small, rugged alternative to USB headers and PCI Express sockets (Fig. 1). This complements the popular IDE-based flash drives for embedded single-board computers (SBC).
Embedding flash chips directly on a board is great for cell phones and other mobile devices where fixed storage is acceptable. But the wide range of removable options, from microSD cards to Compact Flash, will be even more desirable with ever-increasing capacities. Drives of 32 Gbytes are readily available, with large devices coming later in the year.
SanDisk’s 1.8-in., 78-Gbyte solid-state drive (SSD) is an example of where standard form factors are headed in terms of capacity (Fig. 2). They still trail hard drives, but capacity continues to grow as prices drop. The SanDisk drive is available with a SATA interface, making the flash/hard-disk choice more of a cost/performance issue rather than an availability issue.
Meanwhile, hybrid hard disks seem to have been a flash in the pan. Prices are dropping rapidly for flash drives, and their capacities appear to be meeting requirements for fast, low-power storage.
Hard-Disk Capacity Grows
Massive hard-drive capacity is here to address high-definition (HD) content. The compact Fujitsu MHZ2 BT 2.5-in. drive already comes in a 500-Gbyte version that draws only 1.8 W (Fig. 3). Larger-capacity drives will be available later in the year.
The larger 1.5-in. form factor sports 1.5-Tbyte hard drives. Seagate’s Pipeline HD drive is designed for digital video recorders (DVRs) and media PCs. It can support up to 12 simultaneous HD streams. And the Seagate Pipeline HD Pro version delivers even higher reliability.
DVD or Blu-ray?
Want to buy a Blu-ray drive? They will be found in some laptops and consumer movie players, but not too many other products. A few embedded applications can take advantage of Blu-ray’s higher capacity, but DVD drives will likely keep pace to meet designers’ requirements for the next few years.
Optical drives will maintain their usefulness for many applications, but USB, Ethernet, and Wi-Fi have changed the design equation significantly. Optical drives aren’t getting any smaller, and these alternatives use much less space and provide more functionality.
Where Have All The Technologies Gone?
So what happened to storage technologies like MRAM and FRAM? Well, they’re still out there, though existing technologies like flash memory have the lead in capacity. Still, these newer technologies hold certain advantages, such as fast write speeds, and can be found in many embedded microcontrollers.