Using a USB thumb drive for backups?
in [Mac Systems]
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From: Jolly Roger on 20 Dec 2009 16:29 In article <201220091626441223%nospam(a)nospam.invalid>, nospam <nospam(a)nospam.invalid> wrote: > In article <jollyroger-27E138.15074920122009(a)news.individual.net>, > Jolly Roger <jollyroger(a)pobox.com> wrote: > > > I also doubt that the 500ma output of USB ports on a laptop is always a > > continuous stream without fluctuation. > > it's required. read the usb spec. Under all circumstance at every moment of every hour of every day of the year, without fail? Can anyone realistically make such an assurance? I think not. -- Send responses to the relevant news group rather than email to me. E-mail sent to this address may be devoured by my very hungry SPAM filter. Due to Google's refusal to prevent spammers from posting messages through their servers, I often ignore posts from Google Groups. Use a real news client if you want me to see your posts. JR
From: nospam on 20 Dec 2009 16:39 In article <jollyroger-144F53.15292020122009(a)news.individual.net>, Jolly Roger <jollyroger(a)pobox.com> wrote: > > > I also doubt that the 500ma output of USB ports on a laptop is always a > > > continuous stream without fluctuation. > > > > it's required. read the usb spec. > > Under all circumstance at every moment of every hour of every day of the > year, without fail? Can anyone realistically make such an assurance? I > think not. straw man. nobody can guarantee that it will *never* deviate outside the spec. however, in normal use, it must comply with it. <http://www.usb.org/developers/compliance/check_list/compchksys080205.pd f> Can the system supply 0 to 500mA on each of its downstream ports, regardless of whether or not the system or USB is suspended? Can the system maintain VBUS between 4.75 at 5.25V at all of its downstream connectors for DC loads between 0 and 500mA per downstream port? Does the system�s port bypassing limit the maximum voltage droop at any of its downstream ports to 330mV, even when subjected to hot-plug inrush currents with peaks of 7.5A or more? (As of this writing, the highest inrush current the USB-IF has observed from a within spec configuration is 7.40A.) if the answer to any of those is 'no', an explanation must be provided. in other words, it can be assumed that a usb compliant device *does* provide 5v @ 500ma.
From: BreadWithSpam on 20 Dec 2009 18:32 Jolly Roger <jollyroger(a)pobox.com> writes: > In article <201220091238269346%nospam(a)nospam.invalid>, > nospam <nospam(a)nospam.invalid> wrote: > > you haven't measured anything, yet you are so sure it fluctuates?? > > Common sense tells me if the battery power level in a laptop happens to > fluctuate, so will the power supplied to USB ports. Are you saying that > cannot ever happen? Wow, what a tempest. FWIW, all I said when I started with the "USB-powered 2.5 in drive" was that I'd had power problems with an earlier model a few years ago -- it did require the dual cables with my old PB G4. I was skeptical of all USB-powered drives for a long time because of that. I recently got a WD Elements 2.5" drive and it works like an absolute charm on my MBP. Some things to note -- it certainly uses less power, and I believe that the USB ports on the MBP are superior to those on the old G4 -- and lastly, I've never tried to use it while the MBP is running on battery. I've had multiple problems with batteries on the MBP (it's on its third one now). I'd try awfully hard to never use a bus-powered drive on it when not plugged into the wall. But it's awfully nice to be able to plug the drive in with a single cable and be good to go. I hate digging under my desk to get my larger external drives plugged in. So, again, my original point to the OP: try a recent model 2.5" usb-powered drive. You will get vastly more storage for way less money than you'll get with a solid-state thumb-drive. And over the years, I've had thumb drives flake out on me just as I've had hard drives die. These things happen. If it's your primary backup, make sure you have a secondary one, too. That's all, and that goes for *any* medium. -- Plain Bread alone for e-mail, thanks. The rest gets trashed. Are you posting responses that are easy for others to follow? http://www.greenend.org.uk/rjk/2000/06/14/quoting
From: Jolly Roger on 20 Dec 2009 22:08 In article <201220091639266959%nospam(a)nospam.invalid>, nospam <nospam(a)nospam.invalid> wrote: > In article <jollyroger-144F53.15292020122009(a)news.individual.net>, > Jolly Roger <jollyroger(a)pobox.com> wrote: > > > > > I also doubt that the 500ma output of USB ports on a laptop is always a > > > > continuous stream without fluctuation. > > > > > > it's required. read the usb spec. > > > > Under all circumstance at every moment of every hour of every day of the > > year, without fail? Can anyone realistically make such an assurance? I > > think not. > > straw man. nobody can guarantee that it will *never* deviate outside > the spec. And that has been my point all along. Thanks. -- Send responses to the relevant news group rather than email to me. E-mail sent to this address may be devoured by my very hungry SPAM filter. Due to Google's refusal to prevent spammers from posting messages through their servers, I often ignore posts from Google Groups. Use a real news client if you want me to see your posts. JR
From: nospam on 20 Dec 2009 23:20
In article <jollyroger-C71582.21082620122009(a)news.individual.net>, Jolly Roger <jollyroger(a)pobox.com> wrote: > > > > > I also doubt that the 500ma output of USB ports on a laptop is always > > > > > a > > > > > continuous stream without fluctuation. > > > > > > > > it's required. read the usb spec. > > > > > > Under all circumstance at every moment of every hour of every day of the > > > year, without fail? Can anyone realistically make such an assurance? I > > > think not. > > > > straw man. nobody can guarantee that it will *never* deviate outside > > the spec. > > And that has been my point all along. Thanks. you seem to think it happens with regularity. it doesn't. |