Multipathing Software Features (Solaris Express SAN Configuration and Multipathing Guide)

Solaris Express SAN Configuration and Multipathing Guide

Multipathing Software Features

The Solaris Express Developer's Edition OS contains the Sun StorageTek Traffic Manager software. The software is enabled by default for x86-based platforms and optional for SPARC-based platforms. The software contains the following features:

Path management – The Sun StorageTek Traffic Manager software dynamically manages the paths to any storage devices it supports. The addition or removal of paths to a device is done automatically when a path is brought online or removed from a service. This feature enables hosts configured with the software to begin with a single path to a device and add more host controllers, increasing bandwidth and RAS, without changing device names or modifying applications. Sun storage does not require configuration files to manage or databases to keep current. For storage other than Sun, contact your storage vendor for methods to enable support and to ensure it is qualified with the Sun StorageTek Traffic Manager software.
Single Device Instances – Unlike other multipathing solutions, the Sun StorageTek Traffic Manager software is fully integrated with the Solaris Express Developer's Edition OS. The software displays multipath devices as single device instances instead of as one device, or device link, per path. This feature reduces the cost of managing complex storage architectures utilities such as format(1M) or Sun Solaris OS Volume Manager, to “see” one representation of a storage device instead of a separate device for each path.
Failover support – Implementing higher levels of RAS requires redundant host connectivity to storage devices. The Sun StorageTek Traffic Manager software manages the failure of storage paths while maintaining host I/O connectivity through available secondary paths.
Symmetrical/Asymmetrical device support– The Sun StorageTek Traffic Manager software supports the following disk storage devices:
- All Sun disk storage, both symmetric and asymmetric
- All T10/T11 standards-compliant non-Sun symmetrical disk devices
- Many non-Sun asymmetrical disk arrays
  
  Note –
  T10 ALUA support has been added for asymmetrical devices that support this T10 standard. Contact your storage vendor to see whether your device is supported.
I/O load balancing – In addition to providing simple failover support, the Sun StorageTek Traffic Manager software can use any active paths to a storage device to send and receive I/O. With I/O routed through multiple host connections, bandwidth can be increased by the addition of host controllers. The software uses a round-robin load-balancing algorithm by which individual I/O requests are routed to active host controllers in a series one after the other.
Queue depth – SCSI storage arrays present storage to a host in the form of a logical unit number (LUN). LUNs have a finite set of resources available, such as the amount of data that can be stored, as well as the number of active commands that a device or LUN can process at one time. The number of active commands that can be issued before a device blocks further I/O is known as queue depth. When the Sun StorageTek Traffic Manager software is enabled, a single queue is created for each LUN regardless of the number of distinct or separate paths it may have to the host. This feature enables the disk driver to maintain and balance one queue to the LUN, effectively managing queue depth. No other multipathing software available for the Solaris Express Developer's Edition OS has this ability.
stmsboot command – The Solaris Express Developer's Edition OS includes the stmsboot(1M) command, which allows you to enable or disable the Solaris OS Multipathing software on your boot device after the OS installation has been completed. This command is available for both SPARC and x86/x64 systems, and provides support for SAS multipathing with the Solaris Express Developer's Edition OS.

SAS multipathing is not enabled by default in the Solaris Express Developer's Edition OS for either SPARC or x86/x64 hosts, so use of the stmsboot command is required as a post-installation step if you wish to enable Multipathing.

SPARC hosts do not enable multipathing for Fibre Channel devices by default, so use of the stmsboot command is required as a post-installation step.

X86/x64 hosts do enable multipathing of Fibre Channel devices by default, so the use of the stmsboot command is not mandatory as a post-installation step.
Dynamic reconfiguration – The Sun StorageTek Traffic Manager software supports the Solaris Express Developer's Edition OS dynamic reconfiguration (DR).