Tuning Dynamic Multi-Pathing error handling
| Article:HOWTO64325 | | | Created: 2011-12-29 | | | Updated: 2012-04-18 | | | Article URL http://www.symantec.com/docs/HOWTO64325 |
The error handling capabilities of Dynamic Multi-Pathing (DMP) are key to its goal of providing the high availability and performance made possible by multiple I/O paths. Aspects of error handling in DMP can be tuned to get the behavior desired in a particular environment. In most cases though, the default settings for the tunable parameters governing error handling work well and they should be changed with caution. The following examples illustrate tuning decisions related to error handling that an administrator can make, along with the relevant tunable parameters:
Should DMP try to get detailed error information from the HBA interface in order to enable better error analysis (dmp_fast_recovery)?
How many times should DMP retry an I/O on a path when the I/O returns an error but error analysis indicates that the path is not faulty (dmp_retry_count)?
How long should DMP wait after sending a SCSI command before timing out (dmp_scsi_timeout)?
Should DMP detect and avoid intermittently failing paths (dmp_health_time and dmp_path_age)?
How long should DMP wait after a failover, such as with an active-passive array, before commencing I/Os (dmp_delayq_interval)?
How should DMP behave when all paths to a LUN have failed, which in some cases indicates an array undergoing maintenance (dmp_lun_retry_timeout)?
See Dynamic Multi-Pathing SCSI bypass
See Dynamic Multi-Pathing I/O failure handling
See Avoiding suspect paths in Dynamic Multi-Pathing
See Dynamic Multi-Pathing tunable parameters for error handling
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Article URL http://www.symantec.com/docs/HOWTO64325
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