13 comment

1. Hi,

   How to know speed of my external usb HDD is there any specific command?

   thanks

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2. Ashwani the most reliable method is to copy a big file say 4GB or so.
   From your system to external HDD and check iostat.
   However, your internal HDD should be fast enough and system shouldn’t be loaded.
   I trust this method :)

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3. Interesting, but then, I would like to know more:
   – How to you toggle to higher bit rate when/if possible?
   – How do you link these message to your drives? For instance, you have here “ata3” link, how does this links to any /dev/sd.. ?
   TIA,
   — P

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   1. How to you toggle to higher bit rate when/if possible?

      You need to pass boot time kernel parameters using grub. Search libata.force using this doc. Example to force 1.5G and 3.0G: libata.force=1:3.0G,2:1.5G

      How do you link these message to your drives? For instance, you have here “ata3″ link, how does this links to any /dev/sd.. ?

      You need to go through /sys/class/ata_link. Search for sata_spd file. Use lsscsi command to map ids.

      cat /sys/devices/pci0000:00/0000:00:1f.2/ata3/link3/ata_link/link3/sata_spd
      

      Also

      dmesg | grep -i --color ahci 
      dmesg | grep -i  ahci | grep -i --color Gbps
      

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4. Thanks Vivek.

   By the way, on my Debian squeeze 6.0.5, /sys/class does not contain /ata_link but it contains:

   • scsi_device
   • scsi_disk
   • scsi_generic
   • scsi_host

   I tried to find clues, such as in /sys/class/scsi_device/2\:0\:0\:0/device/, but then I cannot make a link to ata3 or alikes. No sata_spd found yet.

   I have used lsscsi, either, and I have just watched your video and your lsscsi topic.

   I am still unable to link “ata3” to an exact drive, “dmesg|grep” commands didn’t tell much, but thanks to you, I learned some new stuff. :-))

   — Philippe

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5. Philippe,

   Commands discussed here depends upon your bios, hd firmware, motherboard and kernel driver. You need libata driver loaded. Linux ship with various ata driver located in /lib/modules/$(uname -r)/kernel/drivers/ata. Linux will load the correct driver at boot time as per your hardware. The examples output is taken from kernel v3.2.0 running on Debian Linux 6.0.5. For testing purpose try loading backported kernel v3.2.0.

   HTH

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   1. Thanks again.

      FYI, on my plain debian 6.0.5, Linux uses following modules tree:
      ata_generic => libata => scsi_mod
      So kernel v3.2.0 does not seem mandatory for libata
      Linux runs on a Thinkpad T400 laptop (exact model 64741AG).

      –P

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6. To measure the actual speed of an external USB disk:
   I use dd command from dev/null to a file on that USB disk, using block size parameter set to 1MB, and count set to 1000. This creates a 1 GB file, so averages disk speed, and eliminates buffering.
   The above is for write speed
   from a 1 GB file on the USB disk to /dev/null, you can test read speed

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7. Hi Guys,

   My SATA link shows 1.5 GB
   [ 1.204017] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
   However when I check the read write speed I get
   /dev/sda1:
   Timing cached reads: 412 MB in 2.01 seconds = 205.47 MB/sec
   Timing buffered disk reads: 166 MB in 3.03 seconds = 54.80 MB/sec

   And when I copy a file over a 1 Gbps network connection I get around 30 to 40 mbps. What could be the bottle neck as I believe the network file transfer speeds should be able to reach over 105-110 Mbps.

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8. The problem with relying on dmesg is that the message may have dissapeared on systems with a long uptime.

   This can be an alternative:
   $ smartctl -a /dev/sda|grep ^SATA
   SATA Version is: SATA 3.0, 6.0 Gb/s (current: 3.0 Gb/s)

   (on my SATA 1 disk, this line does not appear)

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9. Your post (and some of the comments) inspired me to write this, it prints all ata_link speeds and devices:

   #!/bin/sh
   for i in `grep -l Gbps /sys/class/ata_link/*/sata_spd`; do
    echo Link "${i%/*}" Speed `cat $i`
    cat "${i%/*}"/device/dev*/ata_device/dev*/id | perl -nE 's/([0-9a-f]{2})/print chr hex $1/gie' | echo "    " Device `strings` | cut -f 1-3
   done
   

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   1. Thanks for this script. It clearly printed the hard drive name and speed.

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10. Instead of using
    smartctl -a
    you can use
    smartctl -i for a more compact output. :) For example:

    amal-desktop ~ # smartctl -i /dev/sda
    smartctl 6.2 2013-04-20 r3812 [x86_64-linux-3.11.0-12-generic] (local build)
    Copyright (C) 2002-13, Bruce Allen, Christian Franke, www.smartmontools.org
    
    === START OF INFORMATION SECTION ===
    Model Family:     Hitachi Deskstar T7K250
    Device Model:     HDT722516DLA380
    Serial Number:    VDNE1BTCEB01HV
    LU WWN Device Id: 5 000cca 205e12f45
    Firmware Version: V43OA96A
    User Capacity:    164,696,555,520 bytes [164 GB]
    Sector Size:      512 bytes logical/physical
    Device is:        In smartctl database [for details use: -P show]
    ATA Version is:   ATA/ATAPI-7 T13/1532D revision 1
    Local Time is:    Mon Jun  2 09:46:49 2014 IST
    SMART support is: Available - device has SMART capability.
    SMART support is: Enabled
    ==========
    

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