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
_______________________________________________
users mailing list -- users@lists.fedoraproject.org
To unsubscribe send an email to users-le...@lists.fedoraproject.org
Fedora Code of Conduct: 
https://docs.fedoraproject.org/en-US/project/code-of-conduct/
List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
List Archives: 
https://lists.fedoraproject.org/archives/list/users@lists.fedoraproject.org
Do not reply to spam on the list, report it: 
https://pagure.io/fedora-infrastructure

Reply via email to