Thanks Aryeh, for rephrasing my comment in a more specific way. :) I also recall in the old old days of IDE drives that there was some reason to put two heavily-used drives on different (busses? cables?) and not have them as master&slave on the same bus, for analogous reasons. Or maybe it was the other way around, it's been a while. :)
Thank you for suggesting the other options, I think these drives are strictly USB2.0/3.0 compatible. In the end, I ordered a 7-port powered (4A) hub from Plugable. U$50 shipped from Amazon (no other vendors; US & 26 countries but not Canada; happy I'm on holiday with Amazon Prime :). Amazon ASIN B008ZGKWQI It's coming today and I'm looking forward to lining up the self-powered HDs (except I need more power outlets :). Details on the hub after I describe my methodology. I did check Cyberguys as Paul suggested, and also Cable Wholesale. The consistent advice seemed to be powered hub over ExpressCard, usually because of the power thing. Not sure if they were just trying to save my notebook battery or if it's an issue. I did find a couple of sites with specs on the maximum current output for ExpressCard, it sounds like 1000mA at 3.3V and 1750mA total (though what that means in practise I'm not certain). www.usb.org/developers/expresscard/EC_whitepapers/ExpressCardWP.pdf has those numbers, www.expresscard.org/web/site/standardsummary.jsp doesn't seem to mention it at all. Anyway, I think some ExpressCard cards have an input for additional power. Might not be an issue for self-powered devices, though USB 3.0 bus-powered devices expecting 900mA might have a challenge (Y them to a USB 2.0 port for more current, I guess). The way I used Amazon was to limit it to 4* (/5) ratings and above, then sorted by user rating and looked for the best price near the top of the list. The Plugable has 24x5* and 2x4* ratings, nothing lower. Some of the cheaper units (both hub and ExpressCard) might have an average around 3.5* but it's a mix of 5* ratings with 3* and even 1*. Often the 1* start with "worked great the first 2 months then died" (I find this a common pattern on much of the cheap stuff in general). One person gave the Plugable 1* and upgraded to 5* after getting a replacement unit from the manufacturer (and a whole lot of misinformed abuse from another user). I take your point about the single USB bottleneck on the notebook. In terms of overwhelming the USB 3.0 port on the notebook (my original concern, re-expressed so well by Aryeh), I discussed it with Plugable tech support. Among other things, he reminded me that USB 3.0 bus-powered devices can expect up to 900mA, so the hub's 4A/7port wouldn't support 7 bus-powered HDs (though ignoring current loss to the cable, it's >0.5A expected of USB 2.0 ports). When I asked about a hypothetical 7-self-powered-HDs configuration, he said: >Even the fastest drives we've tested are around 200 mb/sec (a few >high end SSD's might be faster), so 7 of those we're still under >2gb/sec total, well under the theoretical 5gb/sec max for usb 3. which is consistent with my vague recollection "the limiting factor becomes HD interface (within the external unit) not the USB connection" and it's nice to have a number. I didn't realize USB 3.0 was that much faster than a HD though! USB 2.0 has a theoretical max of 480Mb/s I think? I don't expect to put 7 drives on at once, and I don't think he was necessarily recommending it, but I have 2 now and plan to buy a third (plus I have a bus-powered USB 2.0/3.0 drive). It will be really nice if I can hook up all 4 when I want to clean up the files, rather than doing everything at USB 2.0 speeds (2 drives at a time). I also have two bus-powered USB 2.0 drives and if they fit on the hub at the same time it will be fantastic. I realized after typing that, that it adds up to 6 drives. Maybe I do intend to put 7 drives on the hub at once (though it's not my primary goal; three is my goal). My ambitions are expanding to fill the theoretical capability. :) The three bus-powered drives together should take about 1.5A of the 4A supplied (they each will work on a USB 2.0 port so 0.5A max demand?). I don't expect all drives to be transferring at the same time, more likely move files between Drive F and Drive G, while also moving files between Drive H and Drive I while any others are idle. I guess that's 4 at once, I'd settle for seeing all my drives while only having one transfer going at a time. Plugable also have a cute 7-displays video on their blog. Not sure I'd ever have a use for it but they have 6 external displays and 1 network connection, hooked up to their 7-port hub, using their USB-VGA, USB-DVI and USB-Ethernet adapters: http://plugable.com/2012/12/27/latest-technology-for-up-to-8-monitors-on-windows Thanks again for the comments and suggestions. I'll (try to) post when I have some benchmarks on this hub. - - Andrew mailto:[email protected] Monday, December 31, 2012, 4:37:59 AM, you wrote: > I would think that with a USB 3.0 hub, all data transfers would be > going through the one USB 3.0 port on the X220, whereas with an > ExpressCard adapter, it would be going from USB 3.0 port to another. > On desktops, I know it is much faster to directly attach USB 2.0 hard > disk drives via their own USB ports directly to the motherboard or via > a PCI card than it is to place them on a shared hub. I would imagine > it is the same with USB 2.0. > Aside from using an ExpressCard, another possible option might be to > connect the X220 to an ThinkPad Mini Dock Plus Series 3 (FRU > 4338-10U, I believe), which has an eSATA port, and hook up one of > the other external drives to that, assuming it has an eSATA > interface, as well. > You may have to do some benchmarking, though, to determine which > interface is fastest for read-intensive and write-intensive > operations. It could be that it is better to put the source or the > target disk on one interface versus another. > Regards, > Aryeh Goretsky > At 10:00 AM 12/28/2012, you wrote: > >>I have an X220 with one USB 3.0 port. So far all the USB 3.0 devices >>I have are external HDs. Two are self-powered and one is USB >>powered. Any one of them is great when hooked up to the USB 3.0 >>port, but transferring files between drives is very slow (USB 2.0 >>speed of course). I expect to get another self-powered 3.5" drive in >>the next few weeks. >> >>Looking on Amazon.com, I see I essentially have a choice of a 4-port >>USB 3.0 hub, or a 2-port ExpressCard 34/54 card. The former will >>result in four USB 3.0 ports, the latter in three. The card also >>takes up less room in my kit. >> >> From the reviews, it seems none of these devices will give the full >> (4.8?) speed of USB 3.0, but that it may not matter as long as I'm >>hooking up rotating hard drives. Also the ExpressCard at least >>doesn't give enough power to power the small HD, but for now I can >>use the built-in port for that drive. >> >>In terms of cheap, not surprisingly everything has some negative >>reviews, but surprisingly some have pretty high ratings. >> >>I'm seeing a 4-port hub w/2A adapter for U$30 shipped (ASIN >>B005QWY3PU, 4/5*). The related 7-port hub is U$50 shipped. >> >>Of the cheaper hubs, ASIN B007BWTOHU (U$27) seems to have the best >>ratings. >> >>For ExpressCard, ASIN B004YB60KA (54mm) is U$6.45 shipped and some >>negative reviews. Same for ASIN B0046XUMDW (54mm) U$10.76 shipped, >>rated 3.5/5*. There's a bunch in the $10 range. >> >>If I get smart and limit to 4* and better (and Prime), cheapest >>ExpressCard adapter is ASIN B006K25AX4 at $29. Cheapest 4*/Prime hub >>is ASIN B004WM36WG at $26. >> >>My question really, is first if anyone has experience with any of >>these (or another in the <$30 range), and secondly if there are >>significant reasons I should go with ExpressCard vs. Hub and why. >> >>Thanks! >> >>- - >> Andrew mailto:[email protected] _______________________________________________ Thinkpad mailing list [email protected] http://stderr.org/cgi-bin/mailman/listinfo/thinkpad
