Messages in this thread | | | Date | Tue, 31 May 2005 01:21:37 +0200 | From | Rene Herman <> | Subject | External USB2 HDD affects speed hda |
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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.
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