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Re: SATA problems



Rohan Kulkarni wrote:


On 7/3/07, *Rohan Kulkarni* <rohan ak1 gmail com <mailto:rohan ak1 gmail com>> wrote:



    On 7/2/07, *John Wendel* < john wendel metnet navy mil
    <mailto:john wendel metnet navy mil>> wrote:

        Rohan Kulkarni wrote:
        >
        >
        >  On 7/2/07, *Tim* <ignored_mailbox yahoo com au
        <mailto:ignored_mailbox yahoo com au>
        >  <mailto:ignored_mailbox yahoo com au
        <mailto:ignored_mailbox yahoo com au>>> wrote:
        >
        >     On Mon, 2007-07-02 at 19:14 +0530, Rohan Kulkarni wrote:
        >      > My motherboard supports hard disk speed of 150MB/s but i
        get only
        >      > 15MB/s speed
        >
        >     Have you double-checked that the figures you're reading at
        are bits per
        >     second or bytes per second?
        >
        >     --
        >     (This box runs FC5, my others run FC4 & FC6, in case that's
        >     important to the thread.)
        >
        >     Don't send private replies to my address, the mailbox is
        ignored.
        >     I read messages from the public lists.
        >
        >
        >
        >  Hello,
        >            Yes I have checked with the motherboard
        specifications.It
        >  says that it supports
        >            a speed of 150MB/s.It is bytes for second.Though my
        hard disk
        >  supports native command queing my motherboard does not support
        it.
        >
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        >

        It doesn't matter what speed your motherboard (SATA controller)
        supports if the disk speed is slower. What brand/model of disk
        do you
        have? What kernel version? How are you measuring the disk speed?

        Regards,

        John



    Hello,
             I have a Seagate ST3160211AS.It is a Barracuda 160GB hard
    disk with a
             speed of 7200RPM.It supports upto 300MB/s with Native
    Command Queing.I checked the average  speed of copying by copying a
             3GB file from one FAT32 partition to another.I got a
    average speed of around
             15MB/s.I have the kernel 2.6.21-1.3228.fc7
                                                             Thanks...



Can anyone please help me...do i need to update to the latest kernel??or do i need
      to download some drivers.

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You don't really have a problem!

Don't confuse the maximum interface transfer speed (150 MB/s) with your disk transfer speed (approx 40-50 MB/s).

When you copy a file, you read the old file, and then you write the new file, rinse and repeat until done. So your transfer speed is going to be approximately 1/2 to disk speed. And now you need to add in the operating system overhead, allocating blocks for the new file, and all the seek time, moving the disk heads between the old file blocks and the new file blocks.

15 MB/s seems reasonable. On my box, using a single drive, I get a write speed of 30 MB/s for a 3 GB file and a copy speed of 14 MB/s.

Need more speed, get more disks and a raid controller.

Regards,

John























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