Re: SATA problems

[John Wendel <john wendel metnet navy mil>]

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