[mythtv-users] SATA drive speeds

[Robin Hill]

On Wed Sep 27, 2006 at 02:42:33PM -0500, Allan Wilson wrote:

> I have a PIV 3.0 GHz system for my  backend that has a hard time plalying
> back HD content especially when other things are going on. I know this is
> the low end of what it takes to run HD using the processor but reading some
> older posts I came back to the subject of dma and sata support for that
> feature in the linux kernel. Can you set dma on a sata device? What kind of
> speeds should I be getting out of my sata drives? I have the Intel ICH5
> chipset. Running the following commands I get:
> 
> sudo hdparm -d1 /dev/sda
> /dev/sda:
> settign using_dma to 1 (on)
> HDIO_SET_DMA failed: Inappropriate ioctl for device
> 
You don't need to enable DMA for SATA drives. Since all SATA drives
have DMA, and all SATA controllers support it, it's enabled by default.
I also don't think hdparm works at all with SATA drives - IIRC you
should be using sdparm (as they're seen using a SCSI style driver).

> and for a speed test I got:
> 
> sudo hdparm -tT /dev/sda
> /dev/sda:
> Timing cached reads:   2604 MB in  2.00 seconds = 1300.90 MB/sec
> Timing buffered disk reads:  176 MB in  3.02 seconds =  58.29 MB/sec
> /dev/sdb:
> Timing cached reads:   2576 MB in  2.00 seconds = 1287.55 MB/sec
> Timing buffered disk reads:  180 MB in  3.01 seconds =  59.85 MB/sec
> /dev/sdc:
> Timing cached reads:   2588 MB in  2.00 seconds = 1293.55 MB/sec
> Timing buffered disk reads:  190 MB in  3.02 seconds =  62.99 MB/sec
> 
> This speed is pretty constant and I wasn't really doing anything on the hard
> drive when I ran the tests.
> 

There certainly doesn't look to be anything wrong with these speeds.  I
don't see these affecting system performance at all (of course, it
depends on how many processes are accessing the disks simultaneously).

HTH,
        Robin

-- 
     ___        
    ( ' }     |       Robin Hill        <myth at robinhill.me.uk>  |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |
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