Microsoft KB Archive/829304

= Multiple Bus Scans Are Performed When You Hot-Swap SCSI Devices =

Article ID: 829304

Article Last Modified on 10/30/2006

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APPLIES TO


 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional
 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Advanced Server

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Notice


SYMPTOMS
When you hot-swap SCSI devices (such as tape drives) by using a single SCSI slot in your computer, and one or more of the following conditions are true, the system must perform two separate bus scans to process the removal of the old drive and the insertion of the new drive:
 * The devices are from different manufacturers.

-or-
 * The devices are of different models.

-or-
 * The devices have different firmware revisions or other differing characteristics.

Additionally, if this operation is performed on a Microsoft Windows 2000 Server-based computer, an &quot;Unsafe Removal&quot; message is displayed after a hot-swappable SCSI device is removed and a bus scan is performed.

Note You can hot-swap SCSI devices only when this operation is supported by both the device and the SCSI bus. For example, the SCSI controller and the host bus adapter must both be supported.



CAUSE
This issue may occur if both the removal of a SCSI device and the arrival of a new SCSI device occur at the same SCSI address in a single bus scan. This is a design limitation of the current implementation of Scsiport.sys in Microsoft Windows Server 2003, Microsoft Windows XP, and Microsoft Windows 2000. Scsiport has to process the removal of the first device before it can process the arrival of the new device at the same SCSI address. Under the current architecture, there is no mechanism for queuing and serializing these multiple events and then processing them with a single bus scan.



RESOLUTION
To optimally hot-swap a SCSI device in a single hot-swappable SCSI slot (to minimize the number of bus scans), follow these steps:
 * 1) Remove the old SCSI device.
 * 2) Perform a bus rescan to process the device removal.
 * 3) Insert the new SCSI device.
 * 4) Perform a bus rescan to process the device arrival.

Alternatively, you can insert the new SCSI device into a different hot-swappable slot from the slot that the previous SCSI device occupied. To do this, follow these steps:
 * 1) Remove the old SCSI device.
 * 2) Insert the new SCSI device into a different slot.
 * 3) Perform a bus rescan to process both the removal of the old device and the arrival of the new device.

Additional query words: scsi hot swap hot-swap swappable device tape drive different manufacturer hardware slot bus scan multiple

Keywords: kbhardware kbprb KB829304

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