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MetroCluster Fabric - How the storage fabric (backend) works ?

Hello,

How does the 2 fabric FC storage  (2 x switchs Brocade 300E/site) works ?

I know the NVRAM traffic is carried on only one fabric (and in case of trouble, failover on the second fabric)

How the SyncMirror trafic is carried on ? is it carried on only one or on the two ?  how it works ?

If on the two fabric: the traffic is it load balanced on the two or first carried on the first fabric and then on the second (when the first have lot of traffic), or other ?

Thanks for you help

Philippe

Re: MetroCluster Fabric - How the storage fabric (backend) works ?

Both ISLs are used actively and Data ONTAP load balances the disk traffic just like with multi path on standard HA pair or single controller.

BTW, Data ONTAP actually load balances the disks on the 4 FC links it has to the 2 local site switches. You can actually see the amount of traffic on each link with the hostadapater stats command (ONTAP 8.x and diag mode). Short example output from a metrocluster (pool 1 is also used for reads):

Instance instance_nam node_name instance_uui total_reads total_writes bytes_read bytes_writte max_link_dat

                                                      /s           /s         /s           /s         KB/s

      0c           0c                                 71            2    2680439        12455      1000000

      0a           0a                                 75            2    3005309        12455      1000000

      1a           1a                                 82            2    2783193        12455      1000000

      1c           1c                                 66            2    3000638        12455      1000000

      0c           0c                                 92            0    4236440            0      1000000

      0a           0a                                 70            0    2533960            0      1000000

      1a           1a                                 90            0    3530800            0      1000000

      1c           1c                                 67            0    2326480            0      1000000

      0c           0c                                369           84   14839760      7163000      1000000

      0a           0a                                301           82   14385280      7096960      1000000

      1a           1a                                303           77   12389000      6098040      1000000

      1c           1c                                315           88   13357760      7228000      1000000

      0c           0c                                 95           85    6013506     10071688      1000000

      0a           0a                                 70           92    3822857     10309090      1000000

      1a           1a                                103           99    6781298     11525194      1000000

      1c           1c                                 82           88    5537662     10354805      1000000