[Q] How can the physical environment slow a drive down? - Storage

This is a discussion on [Q] How can the physical environment slow a drive down? - Storage ; I'm talking about a rackmount computer (Tyan GT24) with 4 drive cages for SATA drives which plug into a backplane. If I have the drives laid out atop the computer with the SATA cables running over the open case into ...

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Thread: [Q] How can the physical environment slow a drive down?

  1. [Q] How can the physical environment slow a drive down?

    I'm talking about a rackmount computer (Tyan GT24) with 4 drive cages
    for SATA drives which plug into a backplane. If I have the drives laid
    out atop the computer with the SATA cables running over the open case
    into the RAID card, the drives are very fast (70-80 MB/second). Now if I
    merely install the drives into the drive cages in the rackmount while
    keeping them directly connected to the SATA cables (i.e., backplane
    removed), the drives are way slower (20-30 MB/second). This is very
    reproducible behavior and it occurs with not only our 750 GB Seagates
    but also with an Hitachi and WD.

  2. Re: [Q] How can the physical environment slow a drive down?

    Maurice Volaski wrote:
    > I'm talking about a rackmount computer (Tyan GT24) with 4 drive cages
    > for SATA drives which plug into a backplane. If I have the drives laid
    > out atop the computer with the SATA cables running over the open case
    > into the RAID card, the drives are very fast (70-80 MB/second). Now if I
    > merely install the drives into the drive cages in the rackmount while
    > keeping them directly connected to the SATA cables (i.e., backplane
    > removed), the drives are way slower (20-30 MB/second). This is very
    > reproducible behavior and it occurs with not only our 750 GB Seagates
    > but also with an Hitachi and WD.


    One obvious way is when vibration disturbs the disk head enough to cause
    the drive to have to re-read data (in your case, since you're clearly
    streaming data it might have to retry a couple of times per revolution
    before it got everything right). This is reportedly one area in which
    'enterprise' drives work better (i.e., are more resistant to such
    disturbance) than desktop drives, and people have specifically reported
    difficulties in multi-drive enclosures where mechanical coupling allowed
    one drive's vibration to affect other drives.

    No guarantee that this is what you're seeing, but it is one possibility.
    I suppose you could also be getting some kind of electrical
    interference in your cabling in the box that does not occur when the
    cables are spread around outside it, but it's more difficult to see how
    that could generate that level of performance loss that you're experiencing.

    I'm not sure whether 'S.M.A.R.T.' information in the drives includes
    data on the kinds of retries that vibration-related problems would
    produce, but it wouldn't hurt to take a look at before-and-after stats
    in both configurations.

    - bill

  3. Re: [Q] How can the physical environment slow a drive down?

    In article ,
    Bill Todd wrote:

    > Maurice Volaski wrote:
    > > I'm talking about a rackmount computer (Tyan GT24) with 4 drive cages
    > > for SATA drives which plug into a backplane. If I have the drives laid
    > > out atop the computer with the SATA cables running over the open case
    > > into the RAID card, the drives are very fast (70-80 MB/second). Now if I
    > > merely install the drives into the drive cages in the rackmount while
    > > keeping them directly connected to the SATA cables (i.e., backplane
    > > removed), the drives are way slower (20-30 MB/second). This is very
    > > reproducible behavior and it occurs with not only our 750 GB Seagates
    > > but also with an Hitachi and WD.

    >
    > One obvious way is when vibration disturbs the disk head enough to cause
    > the drive to have to re-read data (in your case, since you're clearly
    > streaming data it might have to retry a couple of times per revolution
    > before it got everything right). This is reportedly one area in which
    > 'enterprise' drives work better (i.e., are more resistant to such
    > disturbance) than desktop drives, and people have specifically reported
    > difficulties in multi-drive enclosures where mechanical coupling allowed
    > one drive's vibration to affect other drives.
    >
    > No guarantee that this is what you're seeing, but it is one possibility.


    You are right. It's the fans.

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