I do some work with PDA style data collection, and one bottleneck is the transfer to a PC. at times there are 100+ units that have to be attached to USB, data transfer, repeat. This can take hours, and often there are 100+ people waiting for 'their data' so reducing the time is v.important.
In thinking about this problem, I was wondering how significant the speed of the various components are. my hunch is the USB connection is the slow spot, even if it is usb2 (sometimes it is usb1.) That and the physical handling of the equipment. But I want to test this. My first thought was: plug in a thumb drive and use dd to blast some data back and forth. except that I got very different results from 2 usb memory sticks and a usb/ide HD. which made me realize that my tests might be flawed, even though reading was pretty consistent. I realize that this may be more effort than it is worth - but every time there is a line of cranky people I wonder what things can be done to improve things. I think what I am looking for is a way to read/write over the USB connection that does not actually utilize the storage system on the other side. kinda like what ping does for networking. Also, has anyone seen better/worse usb hardware? as in, might a $20 usb 2 card be somehow 'worse' than an $80 one? Below are times for writing/reading 5mb and a baseline to see how long the zero and null io took. Carl K ++ dd if=/dev/zero of=/media/usb/sda1/foo.dat count=5 bs=1M 5+0 records in 5+0 records out 5242880 bytes (5.2 MB) copied, 25.1132 seconds, 209 kB/s real 0m25.396s user 0m0.008s sys 0m0.348s ++ dd if=/dev/zero of=/media/usb/sdb1/foo.dat count=5 bs=1M 5+0 records in 5+0 records out 5242880 bytes (5.2 MB) copied, 119.508 seconds, 43.9 kB/s real 2m0.147s user 0m0.004s sys 0m0.540s ++ dd if=/dev/zero of=/media/usb/sdc1/foo.dat count=5 bs=1M 5+0 records in 5+0 records out 5242880 bytes (5.2 MB) copied, 0.53498 seconds, 9.8 MB/s real 0m0.554s user 0m0.004s sys 0m0.092s ++ dd if=/media/usb/sda1/foo.dat of=/dev/null 10240+0 records in 10240+0 records out 5242880 bytes (5.2 MB) copied, 0.10355 seconds, 50.6 MB/s real 0m0.115s user 0m0.020s sys 0m0.092s ++ dd if=/media/usb/sdb1/foo.dat of=/dev/null 10240+0 records in 10240+0 records out 5242880 bytes (5.2 MB) copied, 0.103117 seconds, 50.8 MB/s real 0m0.114s user 0m0.028s sys 0m0.084s ++ dd if=/media/usb/sdc1/foo.dat of=/dev/null 10240+0 records in 10240+0 records out 5242880 bytes (5.2 MB) copied, 0.103213 seconds, 50.8 MB/s real 0m0.114s user 0m0.016s sys 0m0.100s [EMAIL PROTECTED]:~# time dd if=/dev/zero of=/dev/null count=10 bs=1M 10485760 bytes (10 MB) copied, 0.00134113 seconds, 7.8 GB/s real 0m0.014s user 0m0.008s sys 0m0.004s ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Linux-usb-users@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
