SanDisk Corp. announced the general availability of two new solid state disk (SSD) drives for netbooks that it said increase random read/write rates by as much as nine times over its first generation netbook SSDs.
SanDisk's unveiled the new drives at Computex, in Taipei. The SSDs use a common method to store writes in cache memory, waiting until the SSD is in an idle state to then lay them down. The method normally uses DRAM cache memory. SanDisk, however, said their new pSSD P2 and pSSD S2 drives use a new technology called nCache, which instead of DRAM, uses nonvolatile NAND flash memory as a cache to store writes more efficiently before laying them down on the drive.
Don Barnetson, senior director of marketing for SanDisk's SSD division, said nCache is superior to DRAM because it won't lose data when a drive is powered down as a traditional cache does, and it won't be forced by operating systems to flush its memory to the drive.
Microsoft Corp.'s Windows operating system tends to issue commands to flush cache to storage devices often when the system is busy, as much as 30 times per second. “So when I'm booting Microsoft Outlook, which on an SSD takes about nine seconds, it has perhaps flushed to cache several hundred times during that time. So the cache had a limited opportunity to do what it's supposed to do, which is delay the writes until later,” Barnetson said.
Because SanDisk's nCache is based on NAND flash and not DRAM, Windows will not force it to flush to the disk, allowing it to hold onto the data for five, 10 or as long as 30 minutes, depending on when the drive's controller detects idle time so as to not disrupt user I/O.
“So we're able to write the data to this very quickly, and then sort that data into the main drive in the background,” Barnetson said.
Barnetson said the P2 and S2 drives have sustained read/write rates of about 70MB/sec. or about twice as fast as a standard 5,400RPM hard disk drive. They also consume about half the power of a standard 5,400RPM drive, he said.
The drives are based on multilevel cell (MLC) flash memory and are available with parallel or serial ATA interfaces.
The new SSDs come in 8GB, 16GB, 32GB and 64GB capacities, with up to 320MB of cache. Barnetson said the 16GB version will have an suggested retail price of about $40 and the 32GB drive will run between $60 and $70.
Engineers from SanDisk and Canonical Ltd., creator of the Ubuntu Linux-based operating system, have worked together on system optimizations for the Gen2 pSSD, resulting in improved system responsiveness and longer battery life, SanDisk said in a statement.
“Canonical is enabling original equipment manufacturers and designers to offer consumers a fantastic user experience with Ubuntu Netbook Remix running on netbooks,” said Chris Kenyon, director of OEM services at Canonical. “Our tests have shown SanDisk second generation pSSD equipped with nCache performing significantly better than a 5,400 RPM HDD, providing Ubuntu users with the speed and stability that they need.”