Secure Path v2.0 for Sun Solaris Installation and Reference Guide

2-4 StorageWorks Secure Path Version 2.0 for Sun Solaris
Compaq Confidential – Need to Know Required
Writer: Cyndi Vaccaro Project: StorageWorks Secure Path Version 2.0 for Sun Solaris Comments:
Part Number: AA-RKYDA-TE File Name: c-ch2 Technical Description.doc Last Saved On: 12/21/99 4:52 PM
bus adapter, RAID controller, FC hub, or any connection hardware causes a
path to fail, Secure Path stops sending I/O to the HBA driver, marks the path
as failed, and assigns the standby path as the online path. After this
reconfiguration, I/O is sent along the new online path. This failure-recovery
process is transparent to applications.
Figure 2-3 shows a Secure Path environment on which a Solaris server has
redundant connections to a RAID storage system.
Solaris
Disk Services
Secure Path
Devices
Host Bus
Adapters
sd0 sd1 sd2
ldLite0
ldLite1 ldLite2
fcaw0
fcaw1
ldLite
Devices
sda
Devices
LUN 0
LUN 1
LUN 2
HSG80
Controllers
mda0 mda1 mda2 mda3
mda4 mda5
Controller 0
Port 1 Port 2
Controller 1
Port 1 Port 2
RAID
Storage
Subsystem
Solaris
Server
SHR-1601
Hub 0 Hub 1
Key
On-line Path
Standby Path
Figure 2-3. Before Path Failover
The RAID storage system has three LUNs and the Solaris server has 3 sd
devices associated with the LUNs. Each device has 2 paths. The online path is
shown in black and the standby in white. In Figure 2-3, the active path is
shown as a solid line. The dashed line is the path that is on standby. (To clarify
this example, each Secure Path device is accessing the LUN through the same
HBA/FC hub/RAID controller. Normally, access to the LUNs would be
balanced over both connections.)
As long as the online path is accessible, the Secure Path devices use this path
for I/O. If the active path fails (due to a problem with the HBA fcaw0, for
example), Secure Path detects the error and stops sending I/O along this path.
It then takes the path offline (marks it failed), brings the standby path online
and redirects I/O to the newly active path as shown in Figure 2-4. The dotted
lines denote the failed path.