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Innovation

End of SATA flash drives?

A reader asks “is the MacBook Air's use of straight NAND chips in place of a hard disk the beginning of the end for hard drives?” No. It's the beginning of the end for SATA flash drives. Here's why.
Written by Robin Harris, Contributor on

A reader asks “is the MacBook Air's use of straight NAND chips in place of a hard disk the beginning of the end for hard drives?” No. It's the beginning of the end for SATA flash drives.

Disk on a chip? The new MacBook air has no disk drive option. It is pure flash in capacities ranging from 64 GB to 256 GB. What is different is that the flash is not packaged in a disk-like can.

Instead, it looks like a DIMM: for fat flash chips on a small PC board.

What's new? Plenty of netbooks use flash soldered on the motherboard. Some high-end storage systems from Oracle and Violin memory use DIMM-like flash in terabyte quantities.

What is new is that it appears Apple, seeking ultimate compactness, is taking a page out of the thumb drive playbook. The interface is at one end, next comes the controller, and then the flash chips.

We'll have to await tear downs to see what controller chip and interface the MBA uses, but it would not be a surprise to see Apple dispense with the not-optimized-for-latency SATA disk interface entirely. There is no reason not to go directly from a PCIe bus to the flash chip controller.

Update: The merry band at ifixit.com has completed their teardown of both MBA models. Here's their take on the MBA's SSD:

The one standout in this proprietary sea is the 64 GB SSD. It's not locked down like the rest of the components, although it is a very slim and unusual form factor (for a hard drive). It's attached to the logic board with what appears to be a new mini-SATA (mSATA) connector, which brings hope to super-slim-laptop-hackers all across the globe. This may enable some crafty tinkerers to rig a larger drive inside the Air, provided they can fit everything within the tight confines of the .68" thick case.

So they didn't drop SATA, but they did lose the drive form factor. End update.

The Storage Bits take Disk drives are so slow that the latency of I/O drivers and SATA interfaces isn't a problem. But with NAND//and it's microsecond access times, suddenly storage stack latency began to matter.

It wasn't long before the first PCI flashcards were marketed. They massively reduced storage stack latency. Today's SATA based SSD's are transitional products. They are bandwidth limited and add unneeded latency.

But they are convenient. There are billions of available SATA interfaces in today's computing infrastructure. SATA-based SSD's make it very easy to get a performance boost with minimal disruption.

We'll have to wait and see what architecture Apple used for its flash storage. But there is no doubt that we will see more flash storage looking like DIMMs instead of disks, and without the SATA interface.

Comments welcome, of course.

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