02-08-2018 06:51 AM
We have a host located 30 miles far from the IBM Storage array, is there any formula on calculating the bandwidth ?
I know that the minimum bandwidth between the controller and the Host would be the peak throughout from all hosts in the site, is there an alternate method for calculation.
02-08-2018 11:32 AM
I think what you are looking for is the throughput, on the FC link. Not the bandwidth. The bandwidth will be the value that the link negotiates at when the host connects to the storage node.
I presume, since you are here on a Brocade BBS that you will have switch ports in between the host(s) and the storage array? If the host logs into the 'controller'(Brocade OEM switch labeled with IBM) at 16Gb, and the switch port communicates with the remote switch port at 8Gb, and the storage port negotiates with the remote switch at 8Gb, then the 'bandwidth' of the total link will still be 8Gb, even though the ISL between switches is higher.
Now, if you are looking for the throughput, you can run several tools to determine what type of load you can support. First, you should try to calculate the buffers needed for your ISL. Use the command 'portbuffercalc' to determine your number of buffers:
switch:admin> portbuffercalc 9/4 -distance 50 -speed 16 -framesize 2112
This will most return an absurd high number of buffers required. Don't worry, unless your storage and hosts can support line rate you don't require a full compliment of buffers. Note that it's almost impossible to have a frame size of 2112, so you may want to use a smaller number like 1200.
Now configure your ports using the static number of buffers:
switch:admin> portcfglongdistance 9/4 LS 1 -buffers 424
Or, you may let the Brocade switch configure the number of buffers based on distance:
switch:admin> portcfglongdistance 9/4 LS 1 -distance 50
Or, you can let the switch do it all by determining the buffers given during link init.
switch:admin> portcfglongdistance 9/4 LD 1 -distance 50
After that, it's best to characterize the the link under actual conditions. This can be done using the Brocade Flow Vision suite of tools, and the Flow Generator to simulate traffic between ports. Note, that this does not characterize the host to switch, or the switch to storage capability, even though it does use the PIDs which are logged in. It just characterizes the FC path from source to destination. This is an example from the manual:
switch4:admin> flow --control -simport 1/1 -enable
switch5:admin> flow --control -simport 1/2 -enable (*<--On the remote switch*)
switch4:admin> flow --create flowcase1 -feature generator
-ingrport 1/1 -srcdev 0x040100 -dstdev 0x050200 (*use actual PID values from the login of the devices*)
switch4:admin> flow --show flowCase1
See the FOS Flow Vision documentation for your version for specifics on setting up and running Flow Generator, and the companion tool Flow Monitor to determine the throughput.
02-08-2018 11:44 PM