More on CPU specs of the ReadyNAS Pro

Well, it seems like hdparm is not very accurate. I ran a more simple test and I get similar IO rates to the drive, but the reads from the linux cache are much higher than what hdparm reports. I'm still suspicious as what the heck hdparm does with my USB drives.

This is what I did:

# First create a 1GB file:
dd if=/dev/zero of=gigfile bs=1M count=1000

# Flush the file to disk
sync

# purge the cache
echo 3 | sudo tee /proc/sys/vm/drop_caches

# see the cache is mostly empty
free -m

# time the physical read case
time cat gigfile > /dev/null

# see that the big file is now in cache
free -m

# time the cache read
time cat gigfile > /dev/null

If I divide 1000 / by the elapsed time I get a physical read number similar to hdparm. For me about 300MB/sec. I think the difference there is probably the drives I'm using. But for the cached read I get over 4000MB/s so I don't understand why hdparm reports only 1900MB/s.

By the way fastfwd, what os rev are you running? I'm running 4.2.21.

thanks,
steve