我买了两个金士顿 USB 棒，一个 8 Gb，一个 32 Gb，不知道它们运行速度是否太慢。看来最大的那个使用 Ext4 运行速度更快。
问题：这两个 USB 运行速度够快吗，还是它们坏了？
问题：为什么一个 USB 驱动器使用 Ext4 时运行速度更快，而另一个却不行？
最后我的观点是与 USB 硬盘或 USB SSD 相比，这两个 USB 棒都采用了非常低成本的技术，但我可能错了。我可以针对所有硬盘和 USB 硬盘运行 hdparm -I，但不能针对两个 USB 棒运行。
我到底为什么要问这个问题？这个问题来自：我可以在 USB 上安装 grub 并将其作为救援磁盘吗？，因为我想知道我是否可以在 USB 驱动器中全新安装 Ubuntu。现在我明白了，这可能取决于这个驱动器的质量。
srs@ubuntu:~$ dmesg | grep -i sdb
[ 3.277465] sd 6:0:0:0: [sdb] 15138816 512-byte logical blocks: (7.75 GB/7.21 GiB)
[ 3.279611] sd 6:0:0:0: [sdb] Write Protect is off
[ 3.279683] sd 6:0:0:0: [sdb] Mode Sense: 2f 00 00 00
[ 3.281741] sd 6:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
[ 3.288860] sdb: sdb1
[ 3.294503] sd 6:0:0:0: [sdb] Attached SCSI removable disk
srs@ubuntu:~$ dmesg | grep -i sdc
[ 175.121840] sd 7:0:0:0: [sdc] 60437492 512-byte logical blocks: (30.9 GB/28.8 GiB)
[ 175.122604] sd 7:0:0:0: [sdc] Write Protect is off
[ 175.122609] sd 7:0:0:0: [sdc] Mode Sense: 45 00 00 00
[ 175.123112] sd 7:0:0:0: [sdc] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
[ 175.127221] sdc: sdc1
[ 175.129221] sd 7:0:0:0: [sdc] Attached SCSI removable disk
srs@ubuntu:~$ sudo hdparm -Tt /dev/sdb1 // sdb1 is a partition with 6 Gb of Fat32
/dev/sdb1:
Timing cached reads: 23052 MB in 2.00 seconds = 11537.47 MB/sec
Timing buffered disk reads: 56 MB in 3.09 seconds = 18.11 MB/sec
srs@ubuntu:~$ sudo hdparm -Tt /dev/sdb2 // sdb2 is a partition with 2 Gb of Ext4
/dev/sdb2:
Timing cached reads: 22668 MB in 2.00 seconds = 11345.37 MB/sec
Timing buffered disk reads: 58 MB in 3.06 seconds = 18.95 MB/sec
srs@ubuntu:~$ sudo hdparm -Tt /dev/sdc1 // sdc1 is a partition with 16 Gb of Fat32
/dev/sdc1:
Timing cached reads: 25156 MB in 2.00 seconds = 12591.29 MB/sec
Timing buffered disk reads: 56 MB in 3.02 seconds = 18.52 MB/sec
srs@ubuntu:~$ sudo hdparm -Tt /dev/sdc2 // sdc2 is a partition with 16 Gb of Ext2
/dev/sdc2:
Timing cached reads: 23476 MB in 2.00 seconds = 11749.46 MB/sec
Timing buffered disk reads: 106 MB in 3.00 seconds = 35.30 MB/sec
