Hybrid Drive - Operation


Unlike most standard hard drives, the hybrid drive in its normal state has its platters at rest, with the motor not consuming power or generating heat. Any data written to the hybrid drive is written to the buffer; there is no risk of data loss in the event of power failure as the buffer's flash memory is not volatile. When reading data from the platters extra data is read and stored in buffer memory (which need not be non-volatile flash memory) in the hope of anticipating future requirements as in any disk cache. Data required for the next boot-up can be stored in the non-volatile buffer before shutting down the computer.

The hybrid drive's platters will spin up to move data from the write buffer to the platters when nearly full, and to read data which is not in the cache.

Early estimates place the actual hard drive usage (when the platters are spinning) at anywhere between 1.25% and 10% for typical single users, although there are obviously situations where platter usage will be much higher, such as the encoding or editing of very large video files, producing reports from a database, etc.

As of early 2008 the special features of hybrid drives were taken advantage of only by Microsoft's Windows Vista and Windows 7 operating systems. The files required for booting are stored in the fast flash memory, reducing boot time by about 11%. Microsoft uses the name ReadyDrive to describe the software side of this technology. While hybrid drives are not required for Vista Premium certification of laptops, some confusion arose as to whether such drives would be mandatory.

The hybrid drive command interface will be standardized in the new Revision 8 of the ATA standard. The ATA-8 draft provides a new set of commands allowing the host to manage the on-board flash memory or other types of non-volatile (NV) cache, for example pinning some LBAs in the NV cache.

In 2010 Seagate released the Momentus XT, which uses so-called "adaptive memory" for its SSD portion, which is not reliant on driver support from the operating system. This removes the need for a special operating system, and the speed benefits can be used by any OS.

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