May 09, 2014, 2:34 AM — Three years after the SATA Express spec was introduced, it's about to come to market in the form of very fast new SSD drives. SATA Express combines Serial ATA and PCI Express that provides PCIe speeds in a SATA form factor.
A change was needed because high-end SSDs have maxed out the bandwidth of SATA III, which is 6Gbits/sec. A faster interface was needed, and PCIe looked like a good choice. PCI Express 3.0 can reach a theoretical max of 15GB/sec when all lanes are used. But PCI Express is a slot on the motherboard. It doesn't use the cabling like SATA, and motherboards might not always have either the slots or high speed slots to support SATA Express.
The solution is a motherboard with SATA Express connectors similar to and backwards compatible with regular SATA drives. The drive connector is a little larger than standard SATA owing to the fact the drive has more lanes for more transfers.
According to the SATA-IO group behind the spec, the SATA Express environment "is pure PCIe." It consists of dual lanes with support for third-generation PCIe speeds. The fastest implementations can offer up to 2GB/s of bandwidth.
While SATA drives use the AHCI interface, SATA Express has the option of either AHCI or NVM Express, a specification designed for SATA Express. AHCI was built in mind for spinning media, while NVM Express is designed specifically for non-volatile memory for lower latency, greater parallelism and improved random read/write performance.
As you can expect, all of this will require new chipsets and motherboards. Those will be coming to market in the next few months. The good news is Microsoft is out front of this with native drivers for both AHCI and NVMe. Unfortunately, it's only in Windows 8.1.
An even more interesting element to SATA Express drives is that while the drives look like your standard 2.5-inch drive, they are actually a pair of mSATA drives slotted on the drive unit. The folks at TechReport have taken a look at one of the first drives to come to market.
They looked at Asustek's Hyper Express drive, which has two 120GB mSATA SSDs striped in a RAID 0 array with dual Gen2 PCIe lanes and dual 6Gbps SATA ports. The drives they saw were beta units and not final. The story says the final product will use an M.2 interface, which is a faster version of mSATA. Another nice plus with two mSATA drives is you can replace them. Instead of removing the whole unit, you can upgrade with two new mSATA or M.2 drives.
Disk stripping is great for getting more speed because data can go through multiple channels, but TechReport points out that TRIM might have a little trouble with two drives made to look as one. The Asus drive they tested didn't support TRIM but it will be by the time the unit ships.
SATA Express looks like a good and quick fix for the bottleneck of SATA IO for everyone from consumers to enterprise systems. Intel will have motherboards chipsets soon and the drive makers will have product out by the end of the year.