Maximum of usb devices is 127 for every usb-controler. http://en.wikipedia.org/wiki/USB
2010/2/22 Clemens Gruber <[email protected]>: > Nice! Is there a maximum number of connected usb-sticks for the > "master-usb-host-controller" of the motherboard? > How many usb sticks would you guys suggest to put together? 1*2*4*8 = 64 > 16GB Usb-Sticks for about 1TB with high performance access times? > The cheapest sticks I have seen until now were at the market for about 1 > Euro per Gigabyte, e.g. the Kingston DataTraveler, isnt that a bit > expensive, paying 1000 Euro (= 1361 USD) for this Terabyte? > > On Mon, 2010-02-22 at 10:02 +0100, Frank A. Stevenson wrote: >> On Mon, 2010-02-22 at 07:11 +0100, sascha wrote: >> >> > The access time for 4 usb sticks is already 0.3ms. Their combined size is >> > 64GB. Take 32 of these groups and you get down to 0.01ms (if it scales >> > indeed). >> > What i was able to test was that it scales up to 16 devices. I got 0.08ms >> > access time with this configuration IIRC. >> > Even if you need 2 or even 4 distinct USB host adaptors to connect 128 >> > devices, you still end up faster and cheaper than with SSD. >> > Besides that, those PCIe SSDs are still more expensive than 2.5inch SSDs. >> > And we certainly do not need hundreds of megabytes per second bandwidth. >> > The write performance is also of no concern. >> > >> > As for the optimization of the USB bus, that comes for free. If you start >> > 4 CPU threads and manage to make each thread access the data blocks of >> > a single device, then the access time improvements scale linearly with the >> > number of devices. >> >> Nice! It seems that USB mass storage should have us well covered for 5K >> requests a seconds :-) I did some further experiments on a single stick, >> and got access times down to 0.4ms when accessing the block device >> directly. (Which means we do away with the filesystem altogether.) >> >> I added the test code to svn: >> tmto-svn/tinkering/various/speedy.cpp >> >> typically you have to do "sudo time ./speedy /dev/sdX" and get timing >> figures for 10000 random reads. (Just under 4 seconds in my test) >> >> F >> >> >> >> _______________________________________________ >> A51 mailing list >> [email protected] >> http://lists.lists.reflextor.com/cgi-bin/mailman/listinfo/a51 > > > _______________________________________________ > A51 mailing list > [email protected] > http://lists.lists.reflextor.com/cgi-bin/mailman/listinfo/a51 > _______________________________________________ A51 mailing list [email protected] http://lists.lists.reflextor.com/cgi-bin/mailman/listinfo/a51
