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maxschlepzig
Asked: 2018-05-19 05:41:23 +0800 CST

在断开连接之前优雅地关闭 USB 磁盘驱动器

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在 Fedora 27 中，当断开外部 USB 磁盘驱动器时，日志记录如下：

May 07 22:29:11 usb 2-3.1: USB disconnect, device number 23
May 07 22:29:11 sd 3:0:0:0: [sdb] Synchronizing SCSI cache
May 07 22:29:11 sd 3:0:0:0: [sdb] Synchronize Cache(10) failed:
                            Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK

对此应该怎么做？

为什么系统/内核在驱动器已断开连接后尝试同步缓存？

是否可以在断开连接之前优雅地关闭 USB 磁盘？例如，使用发出 Synchronize-Cache 命令然后使驱动器减速的命令。

这也许还会减少驱动器上的机械应力，因为旋转磁盘的突然断电不一定是最佳的。

编辑：一个eject /dev/sdb无效，即上面的内核消息仍然显示在设备拔出并且磁盘继续旋转。相反，弹出命令会产生这些内核日志消息：

May 18 17:26:06  ldm_validate_partition_table(): Disk read failed.
May 18 17:26:06  Dev sdb: unable to read RDB block 0
May 18 17:26:06   sdb: unable to read partition table
May 18 17:26:06  ldm_validate_partition_table(): Disk read failed.
May 18 17:26:06  Dev sdb: unable to read RDB block 0
May 18 17:26:06   sdb: unable to read partition table

编辑：关闭磁盘电源udisksctl power-off --block-device /dev/sdb确实有效：

May 19 08:08:21  udisksd[9447]: Successfully sent SCSI command SYNCHRONIZE CACHE 
                                to /dev/sdb
May 19 08:08:21  udisksd[9447]: Successfully sent SCSI command START STOP UNIT
                                to /dev/sdb
May 19 08:08:21  kernel: sd 3:0:0:0: [sdb] Synchronizing SCSI cache
May 19 08:08:21  udisksd[9447]: Powered off /dev/sdb - successfully wrote
         to sysfs path /sys/devices/pci0000:00/0000:00:14.0/usb2/2-3/2-3.1/remove
May 19 08:08:21  kernel: usb 2-3.1: USB disconnect, device number 60

实际上，磁盘随后会断电。

linux hard-disk

1 个回答

  1. Best Answer

    用于udisksctl关闭驱动器：

       power-off
       Arranges for the drive to be safely removed and powered off. On the OS side this includes ensuring that
       no process is using the drive, then requesting that in-flight buffers and caches are committed to stable
       storage. The exact steps for powering off the drive depends on the drive itself and the interconnect
       used. For drives connected through USB, the effect is that the USB device will be deconfigured followed
       by disabling the upstream hub port it is connected to.

    所以例如

    udisksctl power-off --block-device /dev/sdb

    您可以以普通用户身份运行该命令，无需 root 访问权限。
    如果你更喜欢 gui，gnome disks有一个按钮来“关闭这个磁盘”。

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