HP Workstation xw6000 Adaptec SCSI RAID 2120S: Software Reference Guide - Page 185

controller Commands 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. 6-13