topic Re: Queue Full Threshold VA7400 in Disk Enclosures

Queue Full Threshold VA7400

gsb_2 — Wed, 04 Oct 2006 16:01:05 GMT

Anybody know what this should be set to. I have seen it set anywhere from 20 to 750.

Re: Queue Full Threshold VA7400

Sameer_Nirmal — Thu, 05 Oct 2006 00:20:50 GMT

The appropriate value of Queue Full Threshold is mainly depends on the workload putting the various kind of IOs ( random , sequential or read/write intensive etc ).

Setting the value higher or lower than required might affect the system performance. It's max value is 750 per controller port of the array.

There is HP's formula for setting its value
[2*(# disks in RG)] / (controller host ports)

There is another formula I know with which one can estimate the value.

Q= H * P * q * L

H = Number of host connected to the array port
P = Number of host paths connected to the array port
q = Queue depth per LUN ( for HPUX , 8 )
L = Number of LUNs configured on that port being seen by a particular host path.

If you divide the Q/750 * 100, you would get the % of the array port load.

Re: Queue Full Threshold VA7400

gsb_2 — Thu, 05 Oct 2006 10:31:42 GMT

Thanks Sameer for your reply, but with the first formula I get a value of 30 and with the second I get 640. Are they both correct?

Greg

Re: Queue Full Threshold VA7400

Sameer_Nirmal — Thu, 05 Oct 2006 13:54:29 GMT

I am not sure about your setup and how did you get the value of 640.

The HP's formula doesn't take into considertion multiple LUNs ( assumes one lun consisting of multiple disks in the RG) while the second formula does. Thus for a lun and knowing the number of disks underneath it, you can use the HP's formula and then add them for multiple LUNs. Now this calculation should be equal to the value as per second formula.

Refer the user guide at
http://h20000.www2.hp.com/bizsupport/TechSupport/CoreRedirect.jsp?redirectReason=DocIndexPDF&prodSeriesId=89018&targetPage=http%3A%2F%2Fh20000.www2.hp.com%2Fbc%2Fdocs%2Fsupport%2FSupportManual%2Fc00311965%2Fc00311965.pdf