Linux Kernel Finally Being Optimized For SSHDs
The Linux kernel is finally being optimized for use of solid-state hybrid drives (SSHDs) that follow the ATA 3.2 standard.
The SATA standard 3.2 provides hybrid information feature for solid-state hybrid drives, a type of disk drive that features large rotating HDD storage but a smaller solid-state capacity device for frequently used files. The updated Serial ATA standard provides the ability for the driver to provide hints to the SSHD devices about what to place on the SSD/NAND portion and what to place on the traditional rotating magnetic storage area. The SATA 3.2 specification for SSHDs basically allows passing data caching information/requests to the drive while up to this point the kernel/driver has not provided this information to the device for optimal placement of data.
The SATA 3.2 specification was published back in August of 2013 while only now the kernel patches are emerging to make use of the SATA 3.2 SSHD capabilities. The "enable use of Solid State Hybrid Drives" patches allow user-space applications to provide cache hints to the kernel using the ionice syscall. With the patches properly implemented and enabling the SSHD feature, there's a 50% improvement in boot times, 45% improvement in application launch times, a 3x faster browser, and 4x faster SQLite performance.
Jason Akers published the Linux SSHD kernel patches this week on the kernel mailing list and hopefully they'll be finalized in time for merging with the Linux 3.19 kernel. One SSHD drive we reviewed on Phoronix last year was the Seagate ST1000DX001 1TB SSHD.