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Adding additional ISL's within SAN fabric
We have a SAN fabric set up with two Brocade switches (4900 and 5100) and a couple CLARiiON (cx3-40 and cx4-480). We have been running on two ISL's between the two switches. I was looking over the SAN Health report and noticed that the fan out ration was 18.5/1, which from some research was high. So I want to add more ISL's.
Is there a problem with adding a couple more ISL's on-line, without affecting production?
Thanks in advance.
dynamox
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August 3rd, 2010 12:00
i remember there were certain models that required for trunking that all ISL ports are in the same port group ..something to verify.
dynamox
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August 3rd, 2010 12:00
i've added ISLs online without issues. Do you have a trunking license on Brocade ...if you had one you would be able to trunk two ISL into one big "pipe" otherwise you might still have bottlenecks.
http://www.brocade.com/downloads/documents/data_sheets/product_data_sheets/ISLTrunking_DS_07.pdf
RRR
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August 4th, 2010 03:00
It can be done online, as long as you have the trunking license. If you don't have this license load balancing isn't there at all and you'll never know how much traffic travels accross each ISL. You cannot simply take away 1 ISL if you don't have the trunking license. PowerPath may fox communication problems, but since it's not a redundant trunk, I would be careful with separate ISL's. If you have the license, you can add and delete ISL's as you please. To delete ISL's, first disable the specific ports and then reconfigure them for F-use or as a link to another switch.
dynamox
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August 4th, 2010 03:00
good to know, i remember reading that some where and found that requirement kind of odd, logic says you want to distribute the load onto different port groups plus more redundancy that way too.
RRR
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August 4th, 2010 03:00
Trunks in the same ASIC ? A small switch like the 200E has that issue. I believe the bigger 12000's can have trunks accross more ASIC's since software solves that issue since forever, I think. On my 200E however the FOS fixes this now as well in a 6.x FOS (I have 6.2.1.b).
driskollt1
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August 16th, 2010 08:00
If your fabric isn't super busy, then 18.5/1 might be fine.
If you need every port you can get then this might be helpful to keep 18.5:1.
If you don't expect to add any more switches in the near-future...
Split front-end ports of your CLARiiONs between the switches. Zone hosts to the front-end ports that are on the same switch.
If you do tape-backups - Move backup servers and tapes to the same switch - Backups usually do a lot of traffic - so cutting down ISL traffic helps.
By doing this things you could eliminate most ISL traffic and keep 18.5/1
If you expect to add more switches in the future...
Move all your front-end ports, backup servers, tapes, high I/O Servers, etc to one switch. Move all the lower I/O stuff to the other switch. 2 ISLs would probably be fine.
If you just want to leave everything alone...
Install the latest FOS if you don't have it installed.
Clear out port stats for all of your ISL ports. Check over time for increasing counters on these..
tim_rdy_pri 0 Time R_RDY high priority - Not good to have a lot of these
tim_txcrd_z 0 Time BB credit zero (2.5Us ticks) - Might be okay to have these. Not good to have a ton of them.
Also, enabling bottleneck detection helps.
If you don't care and just want to add ISL ports. You can add them online without disruption. I believe Brocade recommends 6:1 oversubscription on ISL ports. I prefer to run my oversubscription higher than that (16:1 - 8:1 - I just reduce the amount of ISL traffic).