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Date:      Sat, 22 Nov 2003 16:24:28 -0500
From:      Scott W <wegster@mindcore.net>
To:        Toomas Aas <toomas.aas@raad.tartu.ee>
Cc:        questions@freebsd.org
Subject:   Re: (Semi)hot swap IDE
Message-ID:  <3FBFD40C.6020703@mindcore.net>
In-Reply-To: <200311222031.hAMKVwm2006917@lv.raad.tartu.ee>
References:  <200311222031.hAMKVwm2006917@lv.raad.tartu.ee>

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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@raad.tartu.ee | http://www.raad.tartu.ee/~toomas/
>* I don't know whether to kill myself or go bowling
>
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>
>  
>

Tomas- this may not be of much help, but hopefully some at least.  I 
dislike IDE and tend ot avoid it like the plague when possible, but:
1.  The 'generic' removeable drive trays for IDE that use a normal IDE 
controller (like attaching to the slave or secondary channel on most 
onboard IDE), with another disk or device attached that's being used, do 
not support removeable devices.  It's _extremely_ likely that you'll 
hang the IDE bus.

2.  Having mentioned #1 already, it's _possible_ that using a secondary 
controller (unsure if this can be the second channel of onboard or not, 
but NOT simply the slave of a given channel with another device), and 
atacontrol, it appears (no, I have not tried this), you can bring the 
controller itself (or channel?) offline, attach or remove the drive, and 
then reattach it.  I'd like to hear more details on this one myself, and 
may have a system I can test it on if I get too bored, but have long ago 
chucked my IDE trays..

3.  Using one of the relatively inexpensive IDE RAID controllers, with 
an enclosure, should allow you to remove and add drives without issues.

4.  Other ideas-
    backup to a single network fileserver equipped with RAID or 
additional drives for backup only.
    other network system- direct to tape
    USB hard drive caddies- have seen these, but not used, converts IDE 
drives to USB device, can re-use existing IDE
    drives for backup via USB port.

Scott




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