On 11 July 2014 20:25, Konstantin Olchanski <[email protected]> wrote:
> On Fri, Jul 11, 2014 at 06:52:07PM -0700, ToddAndMargo wrote: > > On 07/11/2014 06:12 PM, Konstantin Olchanski wrote: > > >On Fri, Jul 11, 2014 at 04:02:09PM -0400, Andrew Z wrote: > > >>> > > >>>... synchronizing a flashing drive (target) with my hard drive > (source) ... > > >>> > > >>>Problem: it is slow -- takes three hours. To help the > > >>>speed issue, I upgraded from USB 2 to USB 3. Backup went > > >>>from 3 hr-15 min to 3 hr-5 min. It is almost faster > > >>>to wipe the stick and rewrite it. > > >>> > > > > > > > > >The main question is this: what is the actual write speed of your USB > flash media? How about the re-write speed? > > (not the same, obviously - as it requires as erase step). > > > > Kanguru SS3: Read 105 MB/sec; 78 MB/sec > > > > > Right, this is almost SSD quality flash, but for some reason, performance > for writing small files > is much worse compared to SSDs. One would think that one could make a USB > flash disk > with same performance as SATA flash (SSD), but perhaps nobody makes the > right > flash controller chip and a dual chip solution is not workable (an SSD > flash controller > behind a USB-to-SATA interface). > > So there are several reasons for this. An SSD has extra hardware to do smart things that a USB stick doesn't. Even if they used the same 'disk' material to write to, the SSD has logic to wear level and a cache to bank small writes so they can be grouped together. A USB stick has none of that and is usually one 'disk' material while the SSD might be 3-4 of them (if it is good, the very cheap ones have 1 which is why writes are horrible). Adding all those parts together and the room needed to keep them cool because writing is 'hot' you end up with a usb stick as large as an external usb drive. > More likely, though, is that the USB form factor, power budget and cooling > capacity > does not permit implentation of full-performance flash disks. > > One would think that USB3 can provide enough juice, but maybe there are > still > problems with cooling and maybe they do not want to make a device that > would > not work in a USB2 slot... > > > K.O. > > > -- Stephen J Smoogen.
