Installation guide

186
EMC Host Connectivity with QLogic Fibre Channel HBAs and CNAs in the Windows Environment
Troubleshooting
\\.\PHYSICALDRIVE1, and \\.\PHYSICALDRIVE2. The number
is assigned during the disk discovery part of the Windows boot
process.
During boot-up, the Windows OS loads the driver for the storage
adapters. Once loaded, the OS performs a SCSI Inquiry command to
obtain information about all the attached storage devices. Each disk
drive it discovers is assigned a number in a semi-biased first come, first
serve fashion based on adapter. (Semi-biased means that the Windows
system always begins with the controller in the lowest-numbered PCI
slot where a storage controller resides. Once the driver for the storage
controller is loaded, the OS selects the adapter in the
lowest-numbered PCI slot to begin the drive discovery process.)
It is this naming convention and the process by which drives are
discovered that makes persistent binding (by definition) impossible
for Windows. Persistent binding requires a continuous logical route
from a storage device object in the Windows host to a volume in an
EMC storage array across the fabric. As mentioned above, each disk
drive is assigned a number in a first-come, first-serve basis. This is
where faults can occur.
Example Imagine this scenario: A host system contains controllers in slots 0, 1,
and 2. Someone removes a cable from the QLogic controller in host
PCI slot 0, then reboots the host.
During reboot, the Windows OS loads the QLogic driver during
reboot and begins disk discovery. Under the scenario presented
above, there are no devices discovered on controller 0, so the OS
moves to the controller in slot 1 and begins naming the disks it finds,
starting with \\.\PHYSICALDRIVE0. Any software applications
accessing \\.\PHSYICALDRIVE0 before the reboot will be unable
to locate their data on the device, because it changed.
The following figure shows the original configuration before the
reboot. adapter 0 is in PCI slot 0 of the Windows host. Each adapter
has four disk devices connected to it, so Windows has assigned the
name \\.\PHYSICALDRIVE0 to the first disk on adapter 0. Each
disk after that is assigned a number in sequence as shown in
Figure 126 on page 187.