Re: [SLE] why go scsi

From: Greg Freemyer (freemyer-ml_at_NorcrossGroup.com)
Date: 11/24/03

  • Next message: Hemond, Steve: "[SLE] CVS issue" 
    To: Suse <suse-linux-e@suse.com>
Date: Mon, 24 Nov 2003 10:57:12 -0500

    On Sun, 2003-11-23 at 18:47, Joe Dufresne wrote:
    > -----BEGIN PGP SIGNED MESSAGE-----
    > Hash: SHA1
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    > I'm working on building a cheap server for a disk/diskless network.
    > right now i've got a compaq proliant, with (4) 550mb scsi drives. I
    > would like to upgrade this to a total of around 100-500 gigs of scsi,
    > with half being mirrored on a raid setup. i'm unsure of the cost of a
    > scsi raid card vs ide raid (need to stfw), but doing a search for
    > cheap/good used scsi drives, i'm looking at 2-300% more in cost over
    > ide. since I've found isa ide controllers for $3, and 500 gigs of ide
    > would run me under $500, what is the advantage of going scsi?
    >
    > I'm beginning to thing that starting with a later AT board and around a
    > 500mhz chip then adding a pair of 250 gig ide drives w/ raid card will
    > not only be cheaper, but give me better overall performance. Am I
    > correct in this line of thinking?
    >
    > Joe
    > - --

    ATA is getting better, but scsi is still superior.

    Most ATA (ide) drives are designed for 20% duty cycle, SCSI 100%.

    On a ATA bus only the Master or Slave can be active at a given time.
    That is why some ATA raid controllers (ie. 3ware at least) only support
    master drives. SCSI does not have a similar limitation.

    ATA drives do not have a command queue. IIRC SCSI has a 7 deep command
    queue. I'm not sure how the command queue is used, but I know it
    effects performance and cost.

    Serial ATA is another good choice. I don't know what duty cycle it is
    designed for, but it does not have the master/slave issues and IIRC it
    has a 3-deep command queue.

    Greg 

    -- 
Greg Freemyer
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