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Will Non-Rotational Drives Create A New SAN Era?

 

Lukas Kubin Submitted by Lukas Kubin on May 5th, 2008

This community has forced me to think of what the next big things in storage areas could be. At first, I thought of protocols, so I wrote an insight about mirroring and some feature-related things. What I forgot completely was the core of current SANs — drives.

Last year, I had a great opportunity to evaluate a DRAM-based array. To me, testing new arrays and running IOmeter tests on them reminds me of my childhood feelings after being given a new Lego box. This time — meaning with the the array, not with the Lego — I was excited by sequential throughput speeds close to 900MBps through a pair of fibres. We changed the test to 100% random pattern and guess what — the performance was almost the same! Sure, it makes sense, no heads are seeking their blocks on disk plates, so everything works at the speed of memory chips. Yet, it was a feeling of crossing a bridge to a new era.

Ask yourself: what factors do you consider when setting up a new storage system? You probably don’t forget to mention performance, expected traffic pattern (random/sequential), calculations of IOPs and number of drives to satisfy the database needs. Storage vendors have undertaken great efforts to design their controllers so they sequentialize the data streams as much as they can, utilizing various caching and disk interface algorithms. What would the world be without these considerations? What new challenges will we face?

The first challenge might be a latency of the connection chain. The HBAs and controller interfaces create significantly higher delays than the storage media itself. Does it matter? I’m not sure. I’ve met a company who couldn’t accept the latency of Fibre Channel infrastructure connecting to that DRAM array. Their application performed time-sensitive decisions based on data stored on the array. Let’s suppose this is not a typical usage, though….

The first adopters of memory based storage media are known already. They’re database systems. The advantage of seek times in random patterns is great. The memory device provides performance of tens or hundreds of traditional rotational drives. Today, like anytime before, the problem is that capacity is many times lower and that price is many times higher than traditional drives. And, like anytime before, both will settle to reasonable levels. (I’m an optimist.)

It’s an open question if there will be any effective usage for non-rotational arrays other than databases. Will we ever use memory devices for sequential, say file-serving applications? Now, that seems like wasting money. Today’s drives with powerful caching and read-ahead algorithms perform well in sequential transfers. The bottleneck is most often at the media level or file-sharing protocol design.

To conclude, I will suggest a tip for a storage vendor: What if you put in some memory devices as an addition to traditional drives in a single box? I don’t mean just increasing a storage controller’s memory, rather I mean a fast disk space configurable as a LUN. Maybe you can go even further and create an intelligent feature, moving the most active random-access disk areas between rotational and memory disk spaces.

 

4 Responses to “Will Non-Rotational Drives Create A New SAN Era?”

  1. Dell-Marc_Farley Says:
    May 7th, 2008 at 12:01 pm

    You know Lukas, your suggestion for a memory LUN was something that was a key component of Convergenet’s design from many years ago when it was Dell’s first big acquisition (it failed). Turned out that it was too difficult to make work back then and the product never came to fruition. I think you will see a lot of creativity applied where non-volatile memory is concerned in the next few years – and it will probably be based on the success or lack thereof of EMC’s products that use the technology.

  2. Lukas Kubin Says:
    May 8th, 2008 at 5:18 am

    Marc, writing the suggestion I thought of few existing products I’ve already touched:

    The active blocks’ migration between two types of storage has been working for several years as a HotZone feature of FalconStor’s IPStor product. Today, there are several types of memory based drives or devices.

    Creating a combination of such two products on the array level might create various interesting applications, I believe.

  3. Stephen Foskett Says:
    May 27th, 2008 at 12:24 pm

    Lukas hits on a real benefit for non-disk storage (massive random I/O) and a real stumbling block (other latency). Nice job!

    I, too, am interested in what would happen if you took dynamic block relocation (as on the EqualLogic and Compellent) and combined it with a few non-disk drives. You could have a real winner on your hands!

  4. Paul Mitchell Says:
    May 27th, 2008 at 4:07 pm

    http://thefutureofstorage.com/archives/41

    We have a U.S. patent application pending
    for an invention that significantly
    improves upon Gigabyte’s i-RAM for PCI slots
    and i-RAM Box products.

    Those products occupy too much space,
    they require obsolete DDR DIMMs, and
    their SATA interface is only 150MB/sec.

    Our invention allows for 2 x DDR2 SO-DIMMs
    to occupy the space of a standard 2.5″
    laptop hard drive, with an integrated ASIC
    to emulate standard SATA power and signal
    connections.

    A jumper block will permit switching between
    a default of 300MB/sec and 600+MB/sec
    (for the future).

    Four (4) of these LapTopRAMDrives(tm) are
    then designed to fit into the backplane
    of a single 5.25″ QuadraPack Q14 from
    Enhance Technology, Inc.:

    http://www.enhance-tech.com/products/multidrive/q14.html

    … allowing a very fast RAID 0.

    4 x LapTopRAMDrives(tm) @ 4GB = 16GB
    which is more than enough for XP/Pro
    plus a standard suite of application software.

    For comparable video demonstrations using
    4 x i-RAM devices, search http://www.youtube.com
    for “i-RAM”. As you watch these, remember
    that the interface speed of each i-RAM device
    is only 150MB/sec. So, double that for
    our invention — the LapTopRAMDrive(tm) –
    when jumpered to operate at 300MB/sec.

    As the article above correctly points out,
    the SATA interface becomes the bottleneck
    because DRAM can easily saturate even
    the fastest SATA/3G interface.

    Interested investors should contact me
    via our Internet website: http://www.supremelaw.org

    We are presently preparing a Request for
    Quotations to IC fabs that can do the R&D
    for a working prototype that is compatible
    with the Q14 (see above).

    Sincerely yours,
    /s/ Paul Andrew Mitchell, Inventor and
    Webmaster, Supreme Law Library
    http://www.supremelaw.org/

    All Rights Reserved without Prejudice

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