USB stick very slow?

x_terminat_or_3 · 08-20-2007, 05:39 PM

Hi all

I have this Kingston USB stick, bought a few months ago on amazon.

According to the specs listed the device's max speed is limited by the USB2.0 protocol, ie 480Mbs

It has come to my attention, however that it is not very fast.

When trying a low-level sequential read of the entire device I get the following results:

11.0MBs or if you want 88Mbs

low-level sequential write of the entire device:

1.7MBs or 13.6Mbs

Now the maximum you can get with USB1 is 15Mbs so the 88Mbs listed above is way above that and proofs that it is using USB2

It is still a far way from the 480Mbs though.

Can this be explained due to system configuration (hardware, memory,os), or are these really the limitations of the usb stick?

dmesg dump pertaining to device

Quote:

usb 5-4: new high speed USB device using ehci_hcd and address 14
usb 5-4: configuration #1 chosen from 1 choice
scsi6 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 14
usb-storage: waiting for device to settle before scanning
usb-storage: device scan complete
scsi 6:0:0:0: Direct-Access Kingston DataTraveler 2.0 PMAP PQ: 0 ANSI: 0 CCS
sd 6:0:0:0: [sdd] 4030464 512-byte hardware sectors (2064 MB)
sd 6:0:0:0: [sdd] Write Protect is off
sd 6:0:0:0: [sdd] Mode Sense: 23 00 00 00
sd 6:0:0:0: [sdd] Assuming drive cache: write through
sd 6:0:0:0: [sdd] 4030464 512-byte hardware sectors (2064 MB)
sd 6:0:0:0: [sdd] Write Protect is off
sd 6:0:0:0: [sdd] Mode Sense: 23 00 00 00
sd 6:0:0:0: [sdd] Assuming drive cache: write through
sdd: sdd1
sd 6:0:0:0: [sdd] Attached SCSI removable disk
sd 6:0:0:0: Attached scsi generic sg4 type 0

Links:

Amazon specs for Kingston Datatraveler 2GB: http://amazon.co.uk/dp/B000ERAON2/...

Kingston Site specs
http://www.kingston.com/flash/dt_chart.asp

Commands used to test:

Low level sequential read:

Code:

dd if=/dev/sdd of=tmp

Low level sequential write:

Code:

dd of=/dev/sdd if=tmp

Electro · 08-20-2007, 07:10 PM

NAND Flash mediums used in USB Flash storage have throughout about a megabyte per second or less. Some manufactures are increasing this throughput by increasing the bandwidth.

USB 2.0 has a speed up to 480 Mbit per second. Though it is a lot lower than this because of huge software overhead.

x_terminat_or_3 · 08-21-2007, 06:01 AM

Thanks Electro, can you elaborate on the software overhead? Note that I did not mount the device, accessing it directly, reading or writing block per block.