05-23-2012 08:29 AM
Hi
Am I right thinking setting the following in /etc/system which sets the QDepth and IO Timeout globally for the HBA's
set sd:sd_io_time=0x3c
Solved! Go to Solution.
05-28-2012 02:36 PM
Hi Kumaran,
Above both are two different things, set sd:sd_io_time is tuning parameter for SCSI Disk Driver which work at Operating System level and are global for all arrays. dmp_queue_depth is tuneable which work at DMP layer , which mean that The maximum number of queued I/O requests on a path during I/O throttling.
More information about I/O Throttling please refer to https://sort.symantec.com/public/documents/sf/5.0/solaris/html/vxvm_admin/ag_ch_dmp_vm31.html#458394
Following are further notes about I/O throttling and what they mean. NOTE: below is from vxdmpadm man page.
throttle
Enables I/O throttling for a path.DMP continues to schedule I/O requests on a path that seems to have failed, but on which an I/O error has not been reported, until the specified limit is reached. DMP then prevents new I/O requests being scheduled on the path, and attempts to reschedule failed I/O requests on other paths. Error detection can be based on the change in response times or pending I/O counts, as follows:
I would also recommend you to review the article http://www.symantec.com/docs/TECH32080 which explain how I/O are processed in vxio driver.
Article http://www.symantec.com/docs/HOWTO45767 will explain more about improving efficiency of DMP in co-existence with SD driver.
I hope above will help.
Regards,
Hafiz
05-24-2012 04:22 AM
Looks the default tuneable value for dmp_queue_depth is "32" but doesn't looks to be enforced eventhough the DOC says it overrides the OS defaults which is /etc/system value
set sd:sd_max_throttle=8
root@server01:/root# vxdmpadm gettune dmp_queue_depth
05-24-2012 06:02 AM
more evidence after setting sd:sd_max_throttle=16
05-28-2012 02:36 PM
Hi Kumaran,
Above both are two different things, set sd:sd_io_time is tuning parameter for SCSI Disk Driver which work at Operating System level and are global for all arrays. dmp_queue_depth is tuneable which work at DMP layer , which mean that The maximum number of queued I/O requests on a path during I/O throttling.
More information about I/O Throttling please refer to https://sort.symantec.com/public/documents/sf/5.0/solaris/html/vxvm_admin/ag_ch_dmp_vm31.html#458394
Following are further notes about I/O throttling and what they mean. NOTE: below is from vxdmpadm man page.
throttle
Enables I/O throttling for a path.DMP continues to schedule I/O requests on a path that seems to have failed, but on which an I/O error has not been reported, until the specified limit is reached. DMP then prevents new I/O requests being scheduled on the path, and attempts to reschedule failed I/O requests on other paths. Error detection can be based on the change in response times or pending I/O counts, as follows:
I would also recommend you to review the article http://www.symantec.com/docs/TECH32080 which explain how I/O are processed in vxio driver.
Article http://www.symantec.com/docs/HOWTO45767 will explain more about improving efficiency of DMP in co-existence with SD driver.
I hope above will help.
Regards,
Hafiz
05-29-2012 01:39 AM
Thanks! that was helpful and a good read!