Re: [ANNOUNCE] [PATCHES] Advanced TCA Hotswap Support in Linux Kernel

[Greg KH]

On Tue, Oct 15, 2002 at 01:46:34PM -0700, Steven Dake wrote:
> The data/telecoms I've talked to require disk hotswap times of less then 
> 20 msec from notification of hotwap to blue led (a light used to 
> indicate the device can be removed).  They would like 10 msec if it 
> could be done.  This is because of how long it takes on a surprise 
> extraction for the hardware to send the signal vs the user to disconnect 
> the hardware.

But what starts the "notification of hotswap"?  Is this driven by the
user somehow, or is it a hardware event that happens out of the blue?

> For legacy systems such as SAFTE hotswap, polling through sg at 10 msec 
> intervals would be extremely painful because of all the context 
> switches.  A timer scheduled every 10 msec to send out a SCSI message 
> and handle a response if there is a hotswap event is a much better course.

What generates the hotswap event?

thanks,

greg k-h