USB 3.0 is transferring too slow

There are multiple points of failure (slowness) here, it seems to me.

(a) Can you try copying a file from hard drive to SSD? And then what speed do you get?
(b) Can you try the SSD in a different computer with USB 3? And then what do you get?

.... Thinkpads_User

25MB/sec is typical USB2.0 speed.  I doubt you would get 640MB/sec (interface speed), since the Crucial m4 maxes out at 500-550MB/sec using an SATA 6Gb interface (http://www.bit-tech.net/hardware/storage/2011/09/08/crucial-m4-vs-vertex-3-new-firmware-face-of/4).  Check what speed your port is actually running at.  If that card plugs into a PCI-e x1 slot, it will be limited to 2.5Gbit/sec in each direction (1 lane bandwidth).

Also, make sure you have the latest firmware fix - there was a release in Aug 2011 that brought the drive up to the maximum.  Before that, it ranked below the middle of the pack.

Make sure your antivirus software is not attempting to scan the files going to and from this drive.  Set the drive in a exclusion list within your AV software.

You may want to temporary disable the AV scanning software during transfers to test if this is the problem or not.

I don't have another USB 3.0 enabled machine to test with. Copying a file on the disk itself, however, is significantly faster, but still not hitting the speed limit. It starts out at 128MB/s, but by the time it finished copying my 4GB test file, it had dropped to 54.9MB/s.

I did disable the power management features, which seemed to help.

Shouldn't I be approaching the speed limit here because I am never leaving the BUS?

Copying TO the SDHC card is still horribly slow. 18.5MB/s.

Copying a folder of MP3's from my hard drive to the SSD appears to be the right speed though. The hard drive is a SATA II, which should top out around 60MB/s read speed, which is what I am getting.

One thing to consider is the card you're reading from.

The copy command uses Windows resources, because I have seen it error out when I try to copy 1 TB from a volume on a RAID controller to another volume on the same RAID array.  You can try your speed tests without the PCI-e card and enclosure; just use the native interface of the card at SATA 3Gbit if you have to.  At this point, you don't know if it's the drive, the card, the enclosure, or something else.

xema:

The card I am reading from is a class 10 SDHC. Does that limit the speed? IF so, to what? If SDHC Class 10 cards can only go USB 2.0 speeds, I am taking all this crap back to the store and getting my $100 back. :-)

DrDammit;
SDHC class 10 have a minimum transfer rate of  10 MB/s.
Your speed limit is the card, getting 25 MB/s means it's working at more than twice the minimum specs.

You can't get more speed from any storage device by plugging it to a faster connection. The speed limit is defined by the storage device.

OK. So, SDHC cards will be the same speed on USB 2.0 as they will be on USB 3.0 then, correct? USB 2.0 Can reach 25MB/s?

Class 10 SDHC cards have a minimum 10MB/s, but appear to top out at 25MB/s. So, since USB 2.0 tops out at 60MB/s, USB 2.0 is sufficient for my setup. The USB 3.0 equipment was returned because it was pretty much worthless since the source disk is what had the speed limit that was slower than USB 2.0 speeds.