Messages in this thread | | | Subject | Re: rescan scsi | Date | Sat, 21 Jun 1997 11:10:04 +0200 (MET DST) | From | (Rogier Wolff) |
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docwhat@gerf.org ;The Doctor What wrote: > > I have a question....why do people say NOT to add scsi devices on the > fly to a system? I thought that was (inpart) the point of SCSI? > > The only things I can think of is: > 1) The device generates a "startup" message that does evil things to > the SCSI card. (Which doesn't make sense, since I always turn off > external scsi devices if I'm not using them for an extended period of time). > 2) There is a chance of an electrical discharge that frys hardware....
You are running more than a WATT of power to the terminator. Disconnecting that might cause inductance to generate voltages that are much too high for computer components.
As the disclaimer in the kernel says: You're not supposed to hot-swap devices. You are maybe allowed to turn off devices that are not used for longer periods. I have an external ROM burner and a scanner, and those only get turned on whenever I use them.
There are also systems that have special hot-swap slots (RAID systems come to mind).... These can be safely hot-swapped as the designers assume responsibiltiy that they took care of all issues related to the hot swapping....
In practise you can hot-swap SCSI devices with just a small chance of blowing up stuff. At the company a friend works for, they fried an SGI's scsi bus, external CDROM drive, and the internal DAT drive by hotswapping the CDROM. I occasionally hot swap my equipment too. It usually survives.... :-)
Roger.
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