Adaptec RAID 2810SA Software Reference Manual page 171

controller pause_io
To pause all I/O activity on the currently opened controller, use the
controller pause_io command. While I/O activity is paused,
you can make changes to devices attached to the controller without
rebooting. For example, you can add, remove, or change SCSI
channel assignments.
Before using this command, you should consider the following
points:
The controller pause_io command allows a maximum
delay of 150 seconds (that is, 2 1/2 minutes) for all I/O activity
on the currently opened controller. This delay is based on an
internal driver timeout (not on any network timeout) of three
minutes.
The network timeout is client-based, and different clients are
likely to have different timeout values. Thus, pausing all I/O
activity on the open controller can cause network timeouts,
particularly if the specified delay is for more than one minute.
If you find it necessary to pause the system for more than a
minute, then network timeouts are usually preferable to
rebooting.
Taking the maximum delay of 2 1/2 minutes increases the
chances that a network timeout will occur. If you cannot
perform the hardware reconfiguration changes in less than 2
1/2 minutes, then you should shut down the system. Even if
you take the maximum delay, you can usually resume the I/O
sooner. This is the reason for making the pause I/O default
time 2-1/2 minutes.
The safest amount of time (that is, timeouts are unlikely to
occur) to delay I/O operations is no more than 30 seconds.
controller Commands
6-12