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back to article One's speedy, one's a fat boy: WD and Toshiba spin out new HDDs

Toshiba has introduced a 12Gbit/s SAS disk interface AL13 series disk drive, doubling its interface bandwidth compared to previous models, while WD has launched a power-sipping high-capacity drive. Toshiba’s 2.5-inch, 15,000 rpm AL13SX capacities go from 300GB, through 450GB to 600GB. Obviously it's smaller and uses less power …

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  1. lurker

    Maybe I'm ignorant, but?

    What exactly IS the benefit of a 12Gbit/sec interface on a device which tops out at maybe 200MB/sec read speed?

    Faster access to cached data I suppose, but surely the benefit from that 12GB/sec will be relatively small with a 128M cache on a 4GB disk?

    This is a serious question btw, I don't really know my SAS, and I've never really fully understood why companies pay so much more for SAS drives over SATA, though I am sure there must be a reason?

    0 0 Reply
    1. Anonymous Coward
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      Anonymous Coward

      Re: Maybe I'm ignorant, but?

      Raid

      3 1 Reply
      1. lurker
        Reply Icon

        Re: Maybe I'm ignorant, but?

        That doesn't really explain it. There is no reason why RAID would require a much higher interface speed than the disk is capable of. The raid CONTROLLER would obviously require a higher interface speed, but not the drives connected to it.

        2 0 Reply
    2. TitterYeNot
      Reply Icon

      Re: Maybe I'm ignorant, but?

      It allows a SAS controller to rapidly squirt a chunk of data and a queue of commands to a disc's buffer at 12Gbit/sec, then while the disc is (relatively) slowly chundering away doing as it's told, the controller can do the same with the other 7 discs it's hooked up to (for example.) Once the first disk has completed its operations, the controller can then come back to it to retrieve data from its buffer or issue new commands, all while the other disks are getting on with their own tasks.

      In other words, if you have x discs which can only be communicated with one at a time on a bus, each of which can read/write at y GBit/sec, you theoretically want a bus that can cope with x times y Gbit/sec. to maximise disk I/O throughput.

      SCSI and SAS standards were designed with multiple discs and multiuser servers in mind, so are generally better at this sort of thing than SATA, though I believe the difference isn't as great it used to be as some SATA standards now include stuff like command queueing etc.

      3 0 Reply
      1. lurker
        Reply Icon

        Re: Maybe I'm ignorant, but?

        Thanks a lot, very informative answer, cheers for taking the time :).

        However, with SATA, unlike SAS/SCSI, the drives aren't on a shared bus, they are each cabled individually to the controller, rather than being on a chain, so wouldn't a SATA raid controller be able to speak to all drives simultaneously using the full SATA bandwidth? Or do SATA controllers acually share bandwidth between the attached SATA devices?

        I can see how it would make sense though in the scenario you initially described, where a controller could maximise thoughput by interleaving the dumping of drive-ram-buffer-sized chunks of data very quickly over a highspeed interface.

        0 0 Reply
  2. Anonymous Coward
    Anonymous Coward

    TCO *increase*? Really?

    FTA: This is sufficient, WD says, for “customers’ TCO increase and savings for large deployments [to] be millions of dollars per year.”

    I wouldn't be surprised if they said that -- it wouldn't be the first time a vendor did that -- but I'm pretty sure they didn't intend to brag about increasing TCO...

    1 0 Reply
  3. David Austin

    6TB WD Black

    When Is this coming? The Blacks have topped out at 4TB for over 2 years, now...

    0 0 Reply

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