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SDXC cards take on SSDs

The latest release of SD card specs includes ultrahigh speed (UHS-1). With data transfer rates up to 104 MB per second this is competitive with most hard drives. The UHS-1 SD card may be the SSD for the rest of us.

The latest release of SD card specs includes ultrahigh speed (UHS-1). With data transfer speeds up to 104 MB per second this is competitive with most hard drives. Is the UHS SD card the SSD for the rest of us?

Flash cards and disks This is not a stretch. Flashcards have always always had a close association with disk drives.

In fact, the original CompactFlash card used a version of the ATA disk interface. You can even configure several of them into a fast RAID 0 stripe.

SDXC cards are spec'd for a disk-competitive 2 TB maximum capacity. They'll be able to keep up with economical SSD capacities for the next 5 years or more.

The file system But if you want to use UHS-1 cards in a device it has to be formatted with Microsoft's proprietary and patent-pending exFAT file system. Vendors have to buy a license from Microsoft to use it.

So why did Microsoft choose to develop a new file system instead of using NTFS? A paper from the SANS Institute suggests why:

NTFS is not designed for removable media, because it uses a lazy write scheme and is slower to write to a disk than FAT. In a lazy write system output operations are queued and might be delayed as I/O is overlapped. Disengaging the removable media before the writes have completed could leave the file system in an inconsistent state and could become corrupted.

Fortunately, flash cards can be formatted, like disks, with a variety of filesystems, including the MacOS HFS+. While exFAT will own the device-PC data interchange market, you aren't limited to it.

The Storage Bits take It may look like SSDs own the disk replacement opportunity. In fact, the market is wide open: only an estimated 10 million SSD's were sold last year as against over 500 million disk drives.

No, your desktop PC won't be replacing disk drives with SDXC cards anytime soon, if only for reasons of cost. But small notebooks and tablets are naturals for the small form factor SD card.

SD cards have a significant advantage over most SSDs because they are removable. It makes it easy to transfer large volumes of data quickly. A dozen 64 GB SD cards in an overnight letter is a lot of bandwidth.

SD cards have another advantage for people concerned about their privacy. They're small enough to flush down the toilet if the cops are pounding on the door. How will vendors work that message into their marketing?

It is illustrative of technological progress that SSD's - touted for their threat to the disk drive market - could be facing a similar challenge from the high-speed SD card. SSD controllers will continue to have the performance advantage, but for casual users that won't matter much and the competition will be good us consumers.

Of course, UHS-1 means that there must be a UHS-2. That will be interesting.

Comments welcome, of course.


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