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 Post subject: Am i calculating host connection limit correct?
PostPosted: Thu Jan 11, 2018 7:25 pm 

Joined: Tue Mar 14, 2017 4:55 pm
Posts: 9
Looking at the matrix; limits of Fan-out(256) and Fan-in(8). Fan-in refers to a host server port connected to one or more 3PAR ports via FC switch. Fan-out refers to the 3PAR FC port that is connected to more than one host HBA via FC switch

Lets assuming we have a 4 node 8400 and only using the built-in FC ports for host connections and our hosts has 2 hbas each.

64 hosts X 4 3par fc paths = 256

Does that mean the max hosts i can have without getting additional FC adapters is 64? And if i were to use 8 paths then that drops to 32 hosts?

Am i calculating this correctly? Please correct me if im wrong.. im just trying to theoretically figure this out for future planning.


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 Post subject: Re: Am i calculating host connection limit correct?
PostPosted: Fri Jan 12, 2018 6:04 am 

Joined: Wed Nov 09, 2011 12:01 pm
Posts: 221
The 256 is per storage port, you only have one host connection per host per storage port so more like 256 hosts.

Also you can split hosts across node pairs, host1 on node 0+1, host2 on node 2+3 if lower IO.

Personally I consider the 256 limit as being a hard limit rather then a target to aim for in production, it might be fine in a test lab where non of the servers do anything but in real world I'd look more towards 64 or 128 depending on load. ;)


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 Post subject: Re: Am i calculating host connection limit correct?
PostPosted: Wed Jan 17, 2018 1:03 pm 

Joined: Thu Jul 06, 2017 3:28 pm
Posts: 41
ailean wrote:
The 256 is per storage port, you only have one host connection per host per storage port so more like 256 hosts.

Also you can split hosts across node pairs, host1 on node 0+1, host2 on node 2+3 if lower IO.

Personally I consider the 256 limit as being a hard limit rather then a target to aim for in production, it might be fine in a test lab where non of the servers do anything but in real world I'd look more towards 64 or 128 depending on load. ;)



Same here, i don't go by the maximum number of hosts I could connect, its all based on the bandwidth they consume. Also keep in mind to stay below the threshold needed for failover. if a port is 100% saturated and the peer port fails, it won't be able to accept the additional traffic needed.


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