Messages in this thread | | | Date | Wed, 1 Jun 2005 10:18:10 +0200 | From | Pavel Machek <> | Subject | Re: External USB2 HDD affects speed hda |
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On Út 31-05-05 01:21:37, Rene Herman wrote: > Hi Bartlomiej. > > My Maxtor 6Y120P0 on AMD756 (UDMA66) normally gives me 50 MB/s according > to hdparm -t: > > === > # hdparm -t /dev/hda > > /dev/hda: > Timing buffered disk reads: 152 MB in 3.01 seconds = 50.57 MB/sec > === > > However, the second I switch on my external USB2 drive (Western Digital > Essential 160G, connected via a PCI card USB2 controller, on a private IRQ): > > === > usb 1-3: new high speed USB device using ehci_hcd and address 3 > scsi0 : SCSI emulation for USB Mass Storage devices > usb-storage: device found at 3 > usb-storage: waiting for device to settle before scanning > Vendor: WD Model: 1600BB External Rev: 0412 > Type: Direct-Access ANSI SCSI revision: 00 > SCSI device sda: 312581808 512-byte hdwr sectors (160042 MB) > sda: assuming drive cache: write through > SCSI device sda: 312581808 512-byte hdwr sectors (160042 MB) > sda: assuming drive cache: write through > sda: sda1 sda2 > Attached scsi disk sda at scsi0, channel 0, id 0, lun 0 > usb-storage: device scan complete > === > > the hdparm -t result drops down to 42MB/s: > > === > # hdparm -t /dev/hda > > /dev/hda: > Timing buffered disk reads: 130 MB in 3.04 seconds = 42.77 MB/sec > === > > Switching the USB2 HDD off again does not work to bring back the 50 MB/s: > > === > # eject sda > # hdparm -t /dev/hda > > /dev/hda: > Timing buffered disk reads: 128 MB in 3.01 seconds = 42.57 MB/sec > > [ push button ] > > usb 1-3: USB disconnect, address 3 > > # hdparm -t /dev/hda > > /dev/hda: > Timing buffered disk reads: 130 MB in 3.04 seconds = 42.73 MB/sec > === > > After a reboot, it's 50 MB/s again. Any idea what this is? > > The USB HDD is not firing interrupts or anything. It just sits idle. > Fully repeatable on 2.6.11.11 and 2.6.12-rc5.
USB controller generating extra DMA load? Try rmmoding usb to see if it goes away. Pavel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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