On Fri, 18 Jun 2021 at 14:10, Patrick O'Callaghan <pocallag...@gmail.com> wrote:
> On Fri, 2021-06-18 at 09:02 -0300, George N. White III wrote: > > On Fri, 18 Jun 2021 at 06:50, Patrick O'Callaghan > > <pocallag...@gmail.com> > > wrote: > > > > > On Fri, 2021-06-18 at 08:58 +1000, Cameron Simpson wrote: > > > > On 17Jun2021 12:15, Patrick O'Callaghan <pocallag...@gmail.com> > > > > wrote: > > > > > On Thu, 2021-06-17 at 07:20 -0300, George N. White III wrote: > > > > > > > The technical specifications of the drives should mention > > > > > > > startup > > > > > > power > > > > > > management. There may also be some power management in the > > > > > > dock. > > > > > > I've noticed that it is becoming more difficult to find > > > > > > detailed > > > > > > documentation > > > > > > of add-on hardware. At one time you could open the box, > > > > > > identify > > > > > > key > > > > > > IC's > > > > > > and get the spec. sheets, but now you may find a general- > > > > > > purpose > > > > > > CPU. > > > > > > > > > > > > > > > > It's a cheap dock so probably not easy to find any technical > > > > > documentation. One thing I might try is to swap the two drives > > > > > around > > > > > just to see if it's always the same one that causes the delay. > > > > > > > > On the subject of power as raised by George, I had trouble with too > > > > many > > > > USB bus powered drives on the home server. A powered USB 3.1 hub > > > > helps > > > > me out there. Doubtless it has its own limits. > > > > > > The dock has its own power supply. > > > > > > > Is this a full-featured dock with USB and monitor outlets or a > > disk only dock? > > > > It might be useful to compare the rating of the power supply with > > the peak load from the drive spec sheet. Older high RPM drives > > had quite high startup draw. Does the power supply have multiple > > voltages or just one voltage (the latter requires conversion in the > > hub)? If the power supply can't meet the startup requirements of > > two drives then it must be doing some power management. The > > simplest approach would be to provide a delay before starting > > one of the drives. > > Interesting idea. Mine is this model: > > > https://www.amazon.co.uk/gp/product/B06XYJGDTH/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 > > The power block says its output is 3A at 12V. > > The drives are both WD model WD10EZEX, (though the label on one says it > has a 64MB cache and the other doesn't). Both labels say 5VDC, 0.68A > and 12VDC, 0.55A. Looks like the dock's power should be enough. > The spec sheet < https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/wd-blue-hdd/product-brief-western-digital-wd-blue-pc-hdd.pdf > says 12V peak load is 2.5 A. It does take power to spin up to 7500 RPM, and I doubt your supply could survive without staggered startup. > > > Amazon has a popular Sabrent disk-only dock -- one review notes: > > > > Cons > > - when using 2 drives and plugging or unplugging one drive BOTH > > go offline, at least temporarily. NOTE: Seems to be a common limitation > > to all these docks. I have yet to find one that does not behave this > > way. > > Must be the way the SATA bus controller is designed. > > - when plugging in 2 drives, they mount sequentially, meaning you > > have to wait for one to mount before the other will > > My problem is that one drive comes up almost instantly and the other > takes 30 seconds. In fact I can live with that. My real gripe is that > the kernel makes me wait even though the drive is not being accessed. > If it just wants to make the drive available, it should be able to wait > asynchronously. > Agreed, but then you need a way to tell the kernel that it won't need anything from the external drives so it is OK to continue booting. Have you considered automounting the drives? -- George N. White III
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