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hdparm -t --direct /dev/sda3
/dev/sda3:
Timing O_DIRECT disk reads: 2466 MB in 3.00 seconds = 821.73 MB/sec
hdparm -t --direct /dev/sda4
/dev/sda4:
Timing O_DIRECT disk reads: 2466 MB in 3.00 seconds = 821.45 MB/sec
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dd if=/dev/zero of=/mnt/sda3/tempfile bs=1M count=1024 conv=fdatasync |& tail -1
...630 MB/s
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sudo sh -c "/usr/bin/echo 3 > /proc/sys/vm/drop_caches"
dd if=/mnt/sda3/tempfile of=/dev/null bs=1M count=1024 |& tail -1
...1.0 GB/s
Interestingly, mounting NTFS using ntfs3 kernel driver, the speed of accessing it is identical to the speed of the adjacent ext4 partition on the same USB.