Solid State Hybrid Drives (SSHD) combine hard disk drive (HDD) technology with NAND flash Solid-State Drive (SSD) technology. This provides a cost effective compromise between the cheap storage capacity of traditional hard disks and the speed of SSDs. The role of the SSD is to act as a cache by storing frequently accessed data, such as the operating system files.
The first generation of hybrid drives were introduced in 2007 by Seagate and Samsung, with only 128MB or 256MB of flash memory. The first use of the term Solid State Hybrid Drive came in 2010 when Seagate introduced a 500GB drive with 4GB of integrated NAND flash memory. As with all hard disk drive technology problems can occur, from physical failures to logical damage of the data stored on the drive. Although they contain an SSD element, data recovery from a hybrid drive is very similar to a traditional hard disk drive.
Dual Drive Hybrid System
Many systems combine an SSD and an HDD which is often referred to as a dual drive hybrid system, although this is a misnomer. It is in reality usually an SSD upon which the operating system is installed, with the larger hard disk drive used for data storage.
In 2013 Western Digital produced a dual drive unit where a single 2.5” unit contains a 120GB solid state drive with a 1TB hard disk drive, as yet the only device of this type. These are separate drives for use within a laptop with only a single drive bay. Software hybrid volumes can also be created, where an SSD device is used to act as a cache for a traditional hard disk, such as bcache and dm-cache under Linux and Apple’s Fusion Drive.
Hybrid Drive Internals
The NAND flash solid state drive element of the hybrid drive is usually only a few gigabytes in capacity, which is usually enough to act as a cache for the most frequently accessed data used by the operating system. Improved performance is achieved by placing so-called “hot data” in the NAND flash memory in the drive. Decisions regarding the placement of this data is done either entirely by the device, known as self-optimised mode, or through hints provided by the operated system, called host-hinted mode. Support for host-hinted mode in Windows 8.1 and patches for the Linux kernel were made available in 2014.
Hybrid Drive Data Recovery
As with any storage device physical failures can occur, either to the electronics or with the components used in the traditional hard disk drive element of the device. Although failure of the controller board and the traditional hard disk drive are more likely, it is also possible for the solid state drive section to fail. It is unclear whether a failure of the solid state drive will render the hybrid drive unusable, or if it will just operate as a standard hard disk drive, with no caching available.
Logical failures through damage to the on-disk partition structures or the file system, either through user error or data corruption are no less likely than with any other type of storage device. If you hybrid drive fails, DiskEng are able to provide the data recovery solution to suit your requirements.