After plugin an (old) 32 MB USB stick I got the following messages in my syslog, there is one message repeated again : "assuming drive cache: write through" Here's the log: ... Apr 24 10:11:26 n22 usb 2-2: new full speed USB device using uhci_hcd and address 6 Apr 24 10:11:26 n22 usb 2-2: configuration #1 chosen from 1 choice Apr 24 10:11:27 n22 SCSI subsystem initialized Apr 24 10:11:27 n22 Initializing USB Mass Storage driver... Apr 24 10:11:27 n22 scsi0 : SCSI emulation for USB Mass Storage devices Apr 24 10:11:27 n22 usb-storage: device found at 6 Apr 24 10:11:27 n22 usb-storage: waiting for device to settle before scanning Apr 24 10:11:27 n22 usbcore: registered new driver usb-storage Apr 24 10:11:27 n22 USB Mass Storage support registered. Apr 24 10:11:32 n22 Vendor: IBM Model: Memory Key Rev: 4.50 Apr 24 10:11:32 n22 Type: Direct-Access ANSI SCSI revision: 00 Apr 24 10:11:32 n22 usb-storage: device scan complete Apr 24 10:11:32 n22 scsi.agent[30376]: disk at /devices/pci0000:00/0000:00:1d.1/usb2/2-2/2-2:1.0/host0/target0:0:0/0:0:0:0 Apr 24 10:11:32 n22 SCSI device sda: 63424 512-byte hdwr sectors (32 MB) Apr 24 10:11:32 n22 sda: Write Protect is off Apr 24 10:11:32 n22 sda: Mode Sense: 45 00 00 08 Apr 24 10:11:32 n22 sda: assuming drive cache: write through Apr 24 10:11:32 n22 SCSI device sda: 63424 512-byte hdwr sectors (32 MB) Apr 24 10:11:32 n22 sda: Write Protect is off Apr 24 10:11:32 n22 sda: Mode Sense: 45 00 00 08 Apr 24 10:11:32 n22 sda: assuming drive cache: write through Apr 24 10:11:32 n22 sda: sda1 Apr 24 10:11:32 n22 sd 0:0:0:0: Attached scsi removable disk sda ... n22 /usr/src/linux # uname -a Linux n22 2.6.16-gentoo-r3 #10 Sun Apr 23 21:04:53 CEST 2006 i686 Intel(R) Pentium(R) M processor 1700MHz GNU/Linux
Why is this a problem?
It's not a problem, but sometimes such a message indicates a hidden problem/bug. That's why I filed this report with a low severity. So if this behaviour is wanted and/or not harmful this bug can be closed.
This is not a bug; it is normal behavior. It has to do with the way the SCSI and block layers work. Each new device is revalidated (which involves checking its total capacity, the write-protect setting, and the cache setting) when it is first detected and then again when it is registered with the block layer. The duplicated messages may be a little annoying, but they aren't a problem. And believe me, the developers are well aware of them. I'm going to close out this bug report.
Ah, thanks for the comprehensive answer.