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09-03-2006 11:43 PM - last edited on 03-16-2014 07:50 PM by Lisa198503
09-03-2006 11:43 PM - last edited on 03-16-2014 07:50 PM by Lisa198503
What are the maximum values for SCSI queue depth ?
Hi
How can I get the maximum values for the scsi queue depth in HP-UX according to type of disk (internal SCSI disk, XP LUN, VA LUN, EVA LUN, ...) ?
Thanx.
P.S. This thread has been moved from Disk to HP-UX > sysadmin. -HP Forum Moderator
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09-04-2006 07:51 PM
09-04-2006 07:51 PM
Re: What are the maximum values for SCSI queue depth ?
HP-UX default Q-depth value is 8 for a LUN.
You can change it for an individual device using
scsictl scsictl -m queue_depth=xx /dev/rdsk/cxtxdx
The max Q-depth per array port for the following arrays are:
XPxxxx 1024
VA7xxx 750
EVAxxxx 2048
I do not know the values for internal disks but assume them very low!
Cheers
Peter
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09-04-2006 10:59 PM
09-04-2006 10:59 PM
Re: What are the maximum values for SCSI queue depth ?
Maximum queue depth you can set with scsictl command is 256.
from man page of scsictl,
"For devices that support a queue depth greater than the system default, this mode controls how many I/Os the driver will ttempt to queue to the device at any one time. Valid values are (1-255). Some disk
devices will not support the maximum queue depth settable by this command.Setting the queue depth in software to a value larger than the disk can handle will result in I/Os being held off once a QUEUE FULL condition exists on the disk."
sajeer
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09-05-2006 02:02 AM
09-05-2006 02:02 AM
Re: What are the maximum values for SCSI queue depth ?
I know the maximum value accepted by scsictl command is 256. But, as shown in man pages,
"Some disk
devices will not support the maximum queue depth settable by this command.Setting the queue depth in software to a value larger than the disk can handle will result in I/Os being held off once a QUEUE FULL condition exists on the disk."
I'm interested in not setting a value larger than the disk can handle in order to prevent I/Os to be held off.
What is that value ?
I guess that value is different from an internal SCSI disk than a XP LUN.
Where can be found that value ?
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09-05-2006 04:10 AM
09-05-2006 04:10 AM
Re: What are the maximum values for SCSI queue depth ?
However, performance tests for the XP have shown that it is best to keep the Q-depth for a single LUN below 17 and for an XP CHIP port below 222.
Cheers
Peter