"NAND [flash memory] fundamentally has native 4K block sizes. Anything that's not aligned to a 4K block creates extra challenges," Sykes said. "There ends up being background operations to garbage-collect that empty space [in larger file blocks] that isn't fully utilized. And, so that activity is chewing up your bandwidth in the background, and it adds extra wear to the NAND [flash memory]."
According to Dean A. Klein, vice president of memory system development at Micron, Apple's platform seems to perform better with SSDs than Windows systems. "It boots better," he said. "Mac OS does things differently."
When Windows-based PCs boot, the BIOS does "quite a few things" while it's waiting for what would normally be a hard disk drive to spin up, Klein said. "With a MacBook, one thing you'll notice is that it boots up very quick. Our belief is that it's savvy enough to know it has an SSD in it, and it's not waiting for the SSD to spin up, and so takes some shortcuts."
Far agreed that Mac OS X is about 1 percent faster than Vista. But that's not the case when using virtualization applications such as Parallels and VMware's Fusion in Mac OS X 10.5 to run the rival operating system. When running Vista through virtualization at the same time the Mac OS is running, SSD performance is affected.
4KB blocks of data are more efficient
Micron's tests showed that when XP begins writing application-related data, that data is almost never aligned with the beginning of a new NAND page; it begins partway into the page and ends partially through another. "So the controller has to deal with that and come back and clean it up later," Far said. "Vista will start that write on 0 or at 8, for example. So the data structure in Vista is more aligned to 4K blocks."
In NAND flash memory, blocks consists of a number of pages and each page is either 512, 2,048 or 4,096 bytes in size. Therefore, a 4KB block more efficiently fills the memory.
Troy Winslow, marketing manager for the NAND Products Group at Intel, said, "We've even done studies showing 80 percent of all OS requests are in the 4K-to-16K range, yet many SSDs were designed on older controller technology that was requesting large file-size transactions of 128K in size. All SSDs perform best at the smaller file size."
Winslow said benchmark testing on XP and Vista indicated that the less-efficient XP machines show a 10 percent improvement in random input/output operations per second using an SSD instead of a hard drive, while Vista showed a 25 percent improvement under the same conditions.
Pat Wilkison, vice president of marketing and business development at NAND flash memory manufacturer STEC Inc., believes there's no detectable difference in SSDs performance among varying operating systems. "There just has not been any meaningful work done in optimizing for SSD," he said.