Template Version: @(#)sac_nextcase 1.64 07/13/07 SMI
This information is Copyright 2007 Sun Microsystems
1. Introduction
1.1. Project/Component Working Name:
System property to control mpt driver bus release timeout feature
1.2. Name of Document Author/Supplier:
Author: Kevin McInerney
1.3 Date of This Document:
19 September, 2007
4. Technical Description
System property to control mpt driver bus release timeout feature
1. Summary
The LSI SCSI chips driven by the mpt driver have the ability to
monitor bus connections and reset the bus if a connection lasts
longer than a specified timeout. The bus reset has a side effect of
incrementally lowering the transfer rate. The timeout value is
hard-coded in the driver at 15 seconds.
A misbehaving SCSI device may not release the bus before this
timeout and will suffer a lower transfer rate as a consequence.
This has been seen in the field as a tape backup performance
problem. Traces have observed this reserved bus condition lasting
as long as two minutes.
This project addresses the problem with a new system property that
specifies the timeout value.
Patch release level is requested.
2. Discussion
A new system property is proposed to allow modification of the 15
second timer:
mpt-on-bus-time
Each SCSI port can be configured separately. (This feature only
applies to parallel SCSI). Its value is an integer representing the
number of seconds for the timer. The range
will be 0 to 3435, with 0 disabling the feature and 3435 being the
maximum configurable whole-second timer value supported by the chip.
Values greater than the maximum will cause the driver to use the
maximum.
3. Interface Table
INTERFACE COMMITMENT
mpt-on-bus-time system property Committed
4. References
LSI Fusion-MPT Message Passing Interface Specification v1.5.2
http://lagoon.central/docs/rpe-drivers/solaris-kernel-driver-mpt/FusionMPT_MPISpec1-5-2.pdf
PSARC 2001/401 MPT driver (message passing technology)
5. Documentation Changes
We propose to update the mpt(7D) man page to include information
about this property. (The man page currently describes several
similar properties).
6. Resources and Schedule
6.4. Steering Committee requested information
6.4.1. Consolidation C-team Name:
ON
6.5. ARC review type: FastTrack
6.6. ARC Exposure: open
