Crucial m4 And Intel SSD 320: The Other SSD Competitors

Meet Intel's SSD 320, The Postville Refresh

Intel's SSD 320 Series: Something Old, Something New

Intel claims it continues to be satisfied with its current generation of NAND controllers. That's why it was a surprise to see Intel select a third-party solution to drive its 6 Gb/s drives. But while that covers the high-end space, there isn't as much changing in the mainstream lineup.

Intel's SSD 320 uses the same architectural design as the preceding second-gen X25-M (Intel’s X25-M Solid State Drive Reviewed). Both employ a ten-channel architecture based on Intel's PC29AS21BA0 controller, along with the same write algorithms. This is also the same controller seen on the "Soda Creek" SSD 310. So, what's different?

There are four major changes with the SSD 320 Series.

1. 25 nm NAND
2. Larger and faster cache
3. Improved data parity
4. Power protection

Larger and Faster Cache, 64 MB of 166 MHz DRAM on our 300 GB drive

Beyond the move to 25 nm NAND, the SSD 320 features a larger cache that runs 33 MHz faster than the X25-M (G2). In combination with ONFI 2.2 NAND, the SSD 320 claims a sequential write performance of 220 MB/s and 4 KB random write performance of 23 000 IOPS. While not nearly as impressive, sequential read performance sees a slight bump to 270 MB/s (about as much as you can hope for over a 3 Gb/s connection). In comparison, random read performance has increased to 39 500 IOPS.

The two other features Intel is focusing on are really the result of influence from the enterprise space. For many smaller or less mission-critical applications, enterprise customers are turning to MLC as a cost-effective way to get the exceptional performance of an SSD without the price tag associated with SLC-based drives. That's why the X25-M ended up selling so well in the enterprise space, and found itself the centerpiece of caching solutions and tiered storage systems. As a result, Intel is now adding features that enterprise customers find important: data parity and power protection.

Intel also introduces a new form of redundancy with the 320 series. When the firmware detects a failed area of NAND, it automatically maps a new physical NAND location into the logical SSD map. Intel claims that there is sufficient space to allow more than an entire die’s worth of blocks to be recovered, a feature not available for the second-gen X25-M. This is more accurately described as analogous to RAID 4 at the NAND “memory band” level.

Intel's SSD 320, The Third-Gen SSD

The 300 GB SSD 320 sample in our Bakersfield, CA lab has 20 NAND packages, and each package adds 16 GB to the drive's capacity. In total, our 300 GB has 320 GB of raw NAND flash, and like other consumer drives, the SSD 320 series employs ~7% overprovisioning. Hence, this drive is listed as the 300 GB model (279 GiB in Windows). Data parity is already accounted for in the ~7% of over-provisioning.

Separately, Intel adds power loss protection to the SSD 320 drives. But instead of using a super-capacitor, as we've seen from some of OCZ's more enterprise-class drives, the SSD 320 drives use several lower-cost capacitors. This allows Intel to save some board real estate and forgo the cost of an additional component. However, Intel needed to add a detection circuit to complete this design. When a power failure occurs, the circuit sends a signal to the controller on the SSD indicating power loss. The controller then cuts the input power to the drive and uses the remaining power in the capacitors to finish any outstanding transfers in the buffer.

Arguably, the biggest story isn't what Intel has changed architecturally. It's really about the price tag. When it was first introduced, the 80 GB model of the X25-M (G2) cost roughly $225. Thanks to more competition and more efficient manufacturing, prices have fall around $2 per gigabyte. This is right about where prices for the SSD 320-series also happen to fall. Though, at capacities above 80 GB, there are some really good deals. The 120 GB model costs only $1.74 per gigabyte.