John Summerfield wrote: > Mikkel L. Ellertson wrote: >> laptop drive enclosures that are powered this way, and I have to >> plug in the power-only plug and let the drive spin up, before >> plugging in the data plug. I also have a couple of 3-1/2" drive >> enclosures that have their own power supply. Most of them requiring >> turning on the drive power supply before plugging in the USB plug. I >> do have one that works fine plugging in the USB plug before turning >> on the power. But that one does not show up in lsusb before turning >> it on. I gues sit depends on how the electronics are powered, and if >> the firmware handles the drive powering up after the USB interface. > > The order of turning on power should not matter. After a power > failure,them drive is almost certain to be up first. OTOH I'd not wish > to remove the USB cable to power off/power on a drive (I may want it > connected over time, but not necessarily with power). > If the enclosure is properly designed, it should not make any difference. But many of the enclosures are not properly designed. The take shortcuts that save on production costs and/or have other design problems that results in the USB electronics not initializing properly if you power things up in the wrong order. The strange thing is that there does not seem to be a correlation between the price and the performance. I have run into cheap, no-name enclosures that perform well, and more expensive drives that have problems. This is basically a case where theory says one thing, and experience shows something else. This is why some people run into problem when powering up the system with a USB drive connected, or the drive does not work when resuming from suspend. (You can get around it on some desktops by changing a jumper so that the USB socket is still powered during suspend.) Mikkel -- Do not meddle in the affairs of dragons, for thou art crunchy and taste good with Ketchup!
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