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Occasional Contributor
Posts: 8
Registered: ‎08-28-2008

Queue Depth Settings for the Brocade 425/825 in ESX

Could someone tell me what the default QD settings for the 425/825 in an ESX environment?

what is the command to be able to see the QD? i'm thinking of changing the QD settings and i'm wondering if there is a best practice documentation out there?

Super Contributor
Posts: 635
Registered: ‎04-12-2010

Re: Queue Depth Settings for the Brocade 425/825 in ESX

You can use the Brocade Command line Utility BCU to set the queue depth.

bcu> fcpim --qdepth <port_id> <q_depth_value>

You can also set this on the GUI. Keep in mind that increasing the queue depth as result in longer response time of the LUNs.

So have a play to find the right settings for your environment.

I hope this helps,

Andreas

Occasional Contributor
Posts: 8
Registered: ‎08-28-2008

Re: Queue Depth Settings for the Brocade 425/825 in ESX

Thanks Andreas.

is there a rule of thumb when changing the QD? for example, would i have to use multiples of 2, 8, 16 etc?

Super Contributor
Posts: 635
Registered: ‎04-12-2010

Re: Queue Depth Settings for the Brocade 425/825 in ESX

Hello Joel,

sorry for my late answer. I was out of office.

Currently I do not have a rule of thumb because it depends on your storage array and the oversubscription of the storage port and the amout of LUNs on each storage port.

If your QD is too big you will have longer response times on your LUNs and maybe some discards on your SAN switch port which is connected to your array.

Primary check on your array how many outstanding IO it can handle (eq Queue depth).

Then calculate for each server the LUN QD * number of LUNs and create the sum of it. If it is bigger than the total QD of the array then reduce the QD on your servers.

If you are intrested in this topic give the freeware &quot;IOmeter&quot; a try to findout how your storage response in case of heavy load and bigger QDs.

Andreas

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