Hybrid hard drive (HHD) is a type of large-buffer computer hard disk drive. Hybrid Disk Drives, the combination of a standard hard disk drive and a NAND chip, are a budding phenomenon enabled by new features of Microsoft’s Windows Vista operating system. This technology promises to sweep the PC hard drive market.
It is different from standard hard drives in that it uses a smaller solid-state drive (SSD) as a cache. The cache typically uses non-volatile flash memory, but some drives use battery backed volatile RAM (a hybrid RAM disk). The flash memory buffer can speed up repeated reads; a RAM buffer speeds both reads and writes, but must be written to backup storage when power is lost.
Samsung claims that a flash based hybrid offers numerous benefits, chief among them speed of data access and consequent faster computer boot process, decreased power consumption, and improved reliability.
Samsung released the first hybrid drives, primarily for notebook computers, to OEMs in March 2007. A hybrid drive may be created from separate devices, managed by software, such as ReadyBoost.
Why Change the Disk Drive?
* Consumes 10-15% of the power budget in mobile solutions
* Slow power up
-Spin up times can be 2-5 seconds
* Seek and rotational latency is a performance bottleneck
* Fragile, shock prone, low MTBF in mobile systems
-Most common failure point in mobile solutions
-Failure may result in user data loss
Why is a Hybrid Hard Disk Better?
* Reduce Power Consumption
-Read and Write disk data while drive is in a low power state with the spindle stopped
* Faster Boot and Resume
-Instant access to data in NV Cache
* Higher Reliability
-Better shock resistance
-Lower operating duty cycle
Technical Assumptions for Hybrid Disk
* Longhorn* with its advanced memory management is the optimal for caching read data (but not write data)
* The Hybrid Hard Disk NV Cache is the optimal location for write data
* NV Cache should be >= 64MB and we recommend 128MB
* Longhorn* will be able to define data (LBAs) to be Pinned in the NV Cache for Boot and Resume benefits.
System Design with Hybrid Hard Disk
* Design objective: Enable fast boot/resume and save power
-Standard motherboard ATA Interface
* BIOS must exit POST rapidly
-Fast memory check
-Fast Chipset initialization
-Initialize HDD early
* BIOS must pass to boot loader quickly
-Fast PNP detection
-Boot HDD first in boot order
* Main memory => 512MB
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