[PLUG] IDE swap tray info
Bryan Murdock
bmurdock at gmail.com
Tue Jan 4 21:43:27 UTC 2005
On Tue, 4 Jan 2005 12:45:02 -0800, Keith Lofstrom <keithl at kl-ic.com> wrote:
>
> Bryan Murdock writes:
>
> > I feel dumb asking this, but, I bought a cheap IDE removeable drive tray
> > from Fry's today without thinking too much about it. This is for my home
> > computer, I just want to be able to swap a second hard drive in and out, for
> > backups and stuff. There's no way this would be hot swap-able, right? I
> > mean, I'm thinking in Linux I could just unmount it, turn the key (which
> > turns of the power) and slide it right out, but something tells me that
> > probably isn't going to work. Does anyone know for sure?
>
> > Bryan
>
> Bryan: Not a dumb question at all. Only the subject line "dumb
> hardware question" was dumb (irrelevant and insufficent information),
> but then, you warned us. In the future, skip the self-deprecation,
> (you are no dummy, you are here, aren't you?) concentrate on "direct
> and informative". On to your question ...
>
> IDE hotswap is indeed possible, but only with the later 2.4.X series
> of kernels. Alan Cox put code in there to permit live hotswap of IDE
> drives; the 2.5.X and 2.6.X kernel folk took it back out again. I
> think they did it to impress Jodie Foster.
>
> With a 2.4.X kernel from late 2003 or 2004, such as RH9 or Fedora Core 1
> (not 2 or 3!) you can do this:
>
> umount /dev/hde (for example)
> hdparm -b 0 /dev/hde
> (turn key, pull drive, insert drive, turn key)
> hdparm -zb 1 /dev/hde
> mount /dev/hde /mnt/tempdrive
>
> The "hdparm" instruction tristates the bus that the drive is on, to
> protect it from damage. You should only have one drive on the cable.
> The "z" for the re-attach is important, it tells the kernel to rebuild
> the drive parameter table, which is otherwise left over from the previous
> drive.
>
> The kernel developers will probably remain fixated on Jodie Foster, or
> the little voices in their heads, rather than users or Alan Cox, so
> don't count on this being fixed in 2.6.X any time soon. Meanwhile, a
> more modern way to do this is to follow wamorita's suggestion and use
> a USB2 enclosure, where hot swap is supported. The problem with the
> USB2 approach is that a significant number of the chipsets are not
> properly supported by the kernel, and external drives will hang for
> minutes in the middle of transfers. Two known-bad enclosures are the
> Maxtor USB2 enclosure, and the Sanmax InClose USB2 enclosures at Fry's.
> A known-good enclosure is the ViPower, which unfortunately is a little
> hard to find; you may find it at ENU, or you may have to mail-order
> some of these. Go for the slide switch rather than the key switch!
>
> I gave a talk on using swappable hard drives for backups at the March
> 2004 PLUG meeting; I will be presenting an updated version of that
> talk to PANUG later this month, and to the Oregon IEEE Consultant's
> Network (members.eeconsult.org). Some of the information can be found
> at www.keithl.com/linuxbackup.html, and some can be found in a three
> part article about dirvish, starting with the January 2005 Sys Admin
> magazine, available at Powell's Technical and other places.
>
> I hope that answers your question in effusive detail. Note the change
> in subject line - my answer will be in the PLUG email archives forever,
> and I want other Googlers to be able to find it!
Wow, thanks for a very complete answer, specially the tips on avoiding
the wrong USB2 enclosures, I never would have thought those pitfalls
existed. I will definitely check out your articles.
Jodie Foster?!?
:-)
Bryan
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