(Semi)hot swap IDE

anubis anubis357 at optusnet.com.au
Tue Dec 2 01:55:20 PST 2003


On Sun, 23 Nov 2003 06:31 am, Toomas Aas wrote:
> Hello!
>
> I'm looking for a cheap solution to back up a FreeBSD 4.8 machine.
> Cheap meaning that tape drives are out of question. Even external
> FireWire drives are deemed a bit too expensive by the folks for whom
> I'm doing this research.
>
> This leaves one option I can think of - standard IDE drive in one of
> those removable HDD trays. We'd probably use two drives, one being
> active in the machine and the other being kept somewhere out of the
> house for safety. The machine has an integrated Promise TX2 controller
> and two 80 GB drives are currently configured as RAID1 attached to this
> controller. There are two additional (non-RAID) IDE channels on the
> motherboard, one of them has CD-ROM attached to it and the other is
> free - I could attach the backup HD to that.
>
> I've done some web searching and I'm getting controversial results.
> Most of the info I find seems to indicate that IDE devices cannot be
> hot-swapped. At the same time some vendors are trying to sell stuff on
> their web pages which they advertise as "hot swap IDE drive bays". I
> remain skeptical.
>
> If the majority is right and IDE drives cannot be hot swapped, this
> would indicate that we would need to power down the machine every time
> we want to change the backup HDs. This would be less than perfect, but
> since we are cheap we could live with it.
>
> OTOH I read 'man atacontrol' and saw that there are commands like
> 'atacontrol detach' and 'atacontrol attach' which seem to be meant for
> detaching/attaching IDE devices while the machine is running. Does this
> mean that I could actually run 'atacontrol detach <channel>', swap the
> drive and then run 'atacontrol attach <channel>' and be able to use the
> second HD after that? Is anyone doing something like that?
> --
> Toomas Aas | toomas.aas at raad.tartu.ee | http://www.raad.tartu.ee/~toomas/
> * I don't know whether to kill myself or go bowling
>
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We are currently using those removable drive trays for such a purpose.  We 
have the standard vipower racks that have 3 fans and the sliding on/off 
switch.  The drives are hosted  off a standard promise 2 channel ata card, 
non-raid.   We have a script that dismounts the drive then atacontol 
disconnects it.  We then turn off the power via the switch on the rack and 
yank the drive out.  No need to power down.  Putting it in is just the 
opposite.  Put in, turn on and run a script that atacontrol turns it on and 
then mounts it.  We have been using it for about a month without a problem.  
We are testing it in preparation to use it as a replacement for our nightly 
backup to tape drives.  We will still archive to tape or optical for long 
term data storage.

It looks like as with many other things in the freebsd world it just works.
The only potential problem with the whole setup is that we will be rotating 
the disks every day off site and we are not sure about how the drive trays 
and the disks will handle the constant moving around and plugging in and out.
If you are interested send me an e-mail in say march and I can tell you how 
the first couple of months have been.  
Hopefully it will work, or at least we can make it work with a few mods.  We 
stand to save about $20000AUD as opposed to a tape drive and media.




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