I have an external hard drive (/dev/sdc1) mounted at /mount1When running hdparm -tT /dev/sdc1 I get:/dev/sdc1: Timing cached reads:   2246 MB in  2.00 seconds = 1123.75 MB/sec Timing buffered disk reads: 404 MB in  3.00 seconds = 134.56 MB/secNow if I run time sh -c dd if=/dev/zero of=ddfile bs=8k count=10000 && sync at /mount1 I get:10000+0 records in10000+0 records out81920000 bytes (82 MB) copied, 3.30093 s, 24.8 MB/sreal    0m3.971suser    0m0.029ssys 0m0.791sI also use mhddfs to mount multiple hard drives to the same point (including /mount1) - /HDD. If I run time sh -c dd if=/dev/zero of=ddfile bs=8k count=10000 && sync at /HDD I get:10000+0 records in10000+0 records out81920000 bytes (82 MB) copied, 10.2068 s, 8.0 MB/sreal    0m10.929suser    0m0.026ssys 0m1.287sWhat is going on here? Why are the write speeds SO slow?
Why does hdparm and dd show two completely different results?
mount;hard disk;dd;io;hdparm