SDXC cards take on SSDs

SDXC cards take on SSDs

Summary: 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.

Topics: Processors, Hardware, Storage

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  • RE: SDXC cards take on SSDs

    Dream on, those transfer rates are NEVER what you get in the real world =/ .

    USB 2.0 has a supposed Max transfer speed of 480mbps, never in my entire life have I heard of ANYONE getting those speeds from ANY USB 2.0 device. It's the same with SD cards, (and SDXC), you never get those kind of read/write speeds from them.
    • RE: SDXC cards take on SSDs

      You're right about USB 2: that 480 MB/s number is little more than a lie. Why? Because it it is bi-directional bandwidth: if you are writing as well as reading concurrently.

      But USB 3 is spec'd differently and really can handle several hundred MB/s in one direction.

      As for SDXC cards: flash speeds depend on the number and layout of the chips. As time goes on the cards will use more of that theoretical bandwidth.

      Robin Harris
    • RE: SDXC cards take on SSDs

      True: FireWire 400 is still much faster than USB 480, it's chainable etc. I always wondered why USB got more popular....
  • RE: SDXC cards take on SSDs

    The cards may have high data transfer rates, but they will always be limited by the buss they are plugged into. A high speed card is a waste of money unless the computer is capable of transferring data as quickly as the card.
    • RE: SDXC cards take on SSDs

      Correct. That's why USB 3 is so promising: it is really fast and it is quickly spreading, at least in the PC world.

      Robin Harris
      • Flash and Flash

        @Robin Harris

        Once the flash is available for SDXC in capacities AND at price points that anyone would care about they'll simply package it in SSD's albeit perhaps a slower than current SSDs. IOW, by the time such capacity cards are available SDDs will be cheaper as well.

        But it would be a cool way of adding capacity.
  • I've used a CF card as a main drive.

    The performance was acceptable. I thought I could swap cards for different configurations but I never bothered. The size of SD cards is space-saving but easy to misplace if removed. I think I could get a 2.5" HD down the toilet but you could swallow a SD card if given enough motivation.
    Mac Hosehead
  • RE: SDXC cards take on SSDs

    Here's hoping the actual memory becomes available in the not too distant future!

    I'm a photographer. When I'm shooting action I can routinely generate data at 30ish MB/s - on a four year old Nikon D80. Even with good in-camera buffering and fast memory, this can take a little while to clear! Nikon already make models which could in theory generate image data at about this data rate, simply extrapolating from frame rates and resolutions - I'm glad to hear memory might be catching up with this soon.
  • RE: SDXC cards take on SSDs

    I would like to see a 2.5 inch SATA II raid card that supports 6-10 SDXC, there was one a few years ago for SDHC but it ran into a few problems because of the SDHC format that should not be a problem with SDXC, immagine with 10 128GB SDXC cards in raid 0 you'd get 1.28TB of storage and a read write speed of at least 400MB/s sure the thing would cost upwards of 2k (US) but if one memory module goes you wont lose the whole drive just the data, an just immagine 10 2 TB SDXC cards now that would be amazing in a laptop

    another thing that would be nice, even if it didnt support raid it would be nice to have an internal drive that holds 6-10 cards it would be a bit more data security because if one SDXC card fails you would only use the data on the one card
    Feds Against Guns
  • use UHS-1 cards in a device it has to be formatted with ex-Fat

    Sadly ZDNET fails again. Nearly 2 years on and no correction on misleading information.

    The majority of SDXC cards are currently bought to use in SDHC devices and as such are FAT formatted by the device.