slow USB disk writes

Tue Dec 14 21:04:11 UTC 2010

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On 12/14/2010 07:17 AM, Karl Auer wrote:
> Hi all.
> 
> I'm currently backing up about 80GB of data to an external USB drive, a
> fairly new 1TB HDD in a USB2.0 enclosure that is reported as a
> "high-speed device" in my logs:
> 
> Dec 13 23:34:32 karl kernel: [455208.469135] usb 1-3: new high speed USB device using ehci_hcd and address 8
> Dec 13 23:34:32 karl kernel: [455208.604989] usb 1-3: configuration #1 chosen from 1 choice
> Dec 13 23:34:32 karl kernel: [455208.607216] scsi9 : SCSI emulation for USB Mass Storage devices
> Dec 13 23:34:37 karl kernel: [455213.610623] scsi 9:0:0:0: Direct-Access     WDC WD10 EARS-00Y5B1           PQ: 0 ANSI: 2
> Dec 13 23:34:37 karl kernel: [455213.611998] sd 9:0:0:0: Attached scsi generic sg2 type 0
> Dec 13 23:34:37 karl kernel: [455213.613072] sd 9:0:0:0: [sdb] 1953525168 512-byte hardware sectors: (1.00 TB/931 GiB)
> Dec 13 23:34:37 karl kernel: [455213.615354] sd 9:0:0:0: [sdb] Write Protect is off
> Dec 13 23:34:37 karl kernel: [455213.623000]  sdb: sdb1
> Dec 13 23:34:37 karl kernel: [455213.634903] sd 9:0:0:0: [sdb] Attached SCSI disk
> Dec 13 23:34:38 karl kernel: [455214.737309] kjournald starting.  Commit interval 5 seconds
> Dec 13 23:34:38 karl kernel: [455214.738442] EXT3 FS on sdb1, internal journal
> Dec 13 23:34:38 karl kernel: [455214.738451] EXT3-fs: mounted filesystem with writeback data mode.
> 
> I say "currently" because it has been running for about 24 hours and is
> about three-quarters done. Call me picky, but this seems slow to me.
> 
> USB2 should be able to do 30MB/s on a clear day with a fair wind and all
> the stars in the right positions. That's 30 gigabytes in about a
> thousand seconds, but let's say 15 minutes. Allow for my system to be
> running at a tenth of that, thirty GB would take 150 minutes, but let's
> say three hours. My 80GB should have taken no more than about eight
> hours, even by that pessimistic calculation.
> 
> The USB drive is formatted with ext3 and is mounted in "writeback" mode.
> Below is what lsusb says about the device. The packet size looks a bit
> sad, but maybe it's not what I think it is.
> 
> How fast can other people write 80GB to an external USB2.0 HDD? Looking
> for actual experience here, not theories :-)

Here is mine:

(filesystem on destination is VFAT, average rsync transfer (new files)
rate was 37MB)

[21704.450710] usb 2-2: new high speed USB device using ehci_hcd and
address 7
[21704.606309] scsi11 : usb-storage 2-2:1.0
[21705.604275] scsi 11:0:0:0: Direct-Access     Hitachi  HTS545050B9A300
      PQ: 0 ANSI: 2
[21705.605305] sd 11:0:0:0: Attached scsi generic sg4 type 0
[21705.607028] sd 11:0:0:0: [sdd] 976773168 512-byte logical blocks:
(500 GB/465 GiB)
[21705.609989] sd 11:0:0:0: [sdd] Write Protect is off
[21705.609997] sd 11:0:0:0: [sdd] Mode Sense: 38 00 00 00
[21705.610002] sd 11:0:0:0: [sdd] Assuming drive cache: write through
[21705.613252] sd 11:0:0:0: [sdd] Assuming drive cache: write through
[21705.613265]  sdd: sdd1
[21705.636993] sd 11:0:0:0: [sdd] Assuming drive cache: write through
[21705.637003] sd 11:0:0:0: [sdd] Attached SCSI disk

Bus 002 Device 007: ID 1bcf:0c31 Sunplus Innovation Technology Inc.
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0x1bcf Sunplus Innovation Technology Inc.
  idProduct          0x0c31
  bcdDevice            1.08
  iManufacturer           2 Sunplus Innovation Technology.
  iProduct                3 USB to Serial-ATA bridge
  iSerial                 1 FFFACFF0FF090630FB4400F7F6FFFA
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           32
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          4 Bulk Only Configuration
    bmAttributes         0xc0
      Self Powered
    MaxPower                2mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass         8 Mass Storage
      bInterfaceSubClass      6 SCSI
      bInterfaceProtocol     80 Bulk (Zip)
      iInterface              5 Bulk Only Interface
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
Device Qualifier (for other device speed):
  bLength                10
  bDescriptorType         6
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  bNumConfigurations      1
Device Status:     0x0001
  Self Powered

- -- 
Sarunas Burdulis
Systems Administrator
Department of Mathematics, Dartmouth College
http://math.dartmouth.edu/~sarunas
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