SCSI Mid-Level Multipath

Mike S Anderson

Multipath storage device support is not new to Linux. Currently Linux multipath capabilities exist in the volume management layer, block layer, and in the adapter driver layer.

This paper examines an approach to providing multipath device support in the Linux 2.5+ SCSI mid-level. The target audience is anyone interested in multipath storage support or the Linux SCSI sub-system.

The presentation will cover the following:

• Overview of host and device attributes that present multiple paths to storage, current Linux capabilities providing multipath support, and multipath performance issues.
• Details of the SCSI mid-level implementation.
• Results of a mid-level implementation, including performance and behavior under path failure.
• Outstanding issues.
• Future directions (Multipath personalities).