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Exploring Advanced Format Hard Drive Technology

Posted by ScuttleMonkey on from the lift-the-hood-once-in-a-while dept.

MojoKid writes "Hard drive capacities are sometimes broken down by the number of platters and the size of each. The first 1TB drives, for example, used five 200GB platters; current-generation 1TB drives use two 500GB platters. These values, however, only refer to the accessible storage capacity, not the total size of the platter itself. Invisible to the end-user, additional capacity is used to store positional information and for ECC. The latest Advanced Format hard drive technology changes a hard drive's sector size from 512 bytes to 4096 bytes. This allows the ECC data to be stored more efficiently. Advanced Format drives emulate a 512 byte sector size, to keep backwards compatibility intact, by mapping eight logical 512 byte sectors to a single physical sector. Unfortunately, this creates a problem for Windows XP users. The good news is, Western Digital has already solved the problem and HotHardware offers some insight into the technology and how it performs."

5 of 165 comments (clear)

  1. Re:Large sector size good? by forkazoo · · Score: 5, Insightful

    I thought the point was to have a small sector size. With large sectors, say 4096K, a 1K file will actually take up the full 4096K. A 4097K file will take up 8194K. A thousand 1K files will end up taking up 4096000K. I understand that with larger HDD's that this becomes less of an issue, but unless you are dealing with a fewer number of large files, I don't see how this can be more efficient when the size of every file is rounded up to the next 4096K.

    The filesystem's minimum allocation unit size doesn't necessarily need to have a strong relationship with the physical sector size. Some filesystems don't have the behavior of rounding up the consumed space for small files because they will store multiple small files inside a single allocation unit. (IIRC, Reiser is such an FS.)

    Also, we are actually talking about 4 kilobyte sectors. TFS refers to it as 4096k, which would be a 4 megabyte sector. (Which is wildly wrong.) So, worst case for your example of a thousand 1k files is actually 4 megabytes, not 4 gigabytes as you suggest. And, really, if my 2 terabyte drive gets an extra 11% from the more efficient ECC with the 4k sectors, that gives me a free 220000 megabytes, which pretty adequately compensates for the 3 MB I theoretically lose in a worst case filesystem from your example thousand files.

  2. Re:What About Linux Systems? by marcansoft · · Score: 5, Informative

    If Advanced Format drives were true 4k drives (i.e. they didn't lie to the OS and claim they were 512 byte drives), they'd work great on Linux (and not at all on XP). Since they lie, Linux tools will have to be updated to assume the drive lies and default to 4k alignment. Anyway, you can already use manual/advanced settings in most Linux parititioning tools to manually work around the issue.

  3. And for an overview that knows how to do math... by JorDan+Clock · · Score: 5, Informative

    Anandtech has a much better write up on this technology, complete with correct conversions from bits to bytes, knowledge of the difference between 4096 bytes and 4096 kilobytes, and no in-text ads.

  4. Re:512x4=4MB?? by MrMacman2u · · Score: 5, Insightful
    "it's 4 KiB or just 4096 bytes."

    No. Just no.

    Never use the term 'KiB' for kiloBYTES ever again. Just don't do it. I don't CARE if it's "the new standard". Screw that, it's KB KiloBytes.

    This "new" standard mandated by the IEC can eat me.

    1024 bytes IS, and forever will be, 1 KiloByte (KB)
    1000 bits IS, and forever will be, 1 KiloBit (Kb)

    1999 and the IEC can DROP DEAD. I will never. EVER. Use the new """""""""""""standard"""""""""""".

    That said, excellent job highlighting the dreadful editing, inaccuracies like that are so confusing to try and keep straight between what is written and what was MEANT. Thumps up for you!

    --
    This signature is lame.
  5. Re:And for an overview that knows how to do math.. by WrongSizeGlass · · Score: 5, Funny

    That article doesn't sound like fun at all. How are we supposed to mock it if they haven't made multiple errors, typos and other such blunders? We're smug, semi-knowledgeable 'first posters' with nothing better to do than critique articles that we were too lazy to read or too incompetent to write. I'm going to go wait on the homepage to refresh so I can jump into the next thread without a second thought.