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I'm hoping someone can help me here with understanding how a windows file copy differs between a copy using terracopy (or similar) and what that means for contention on my NAS head.

Background:

Server 1 - 2008r2 NAS head with a Stornext volume (client software required to see volume) attached by fiber, teamed 10Gb nic Vlan111 to Cisco Nexus switch, folder shared from the stornext volume.

Server 2 - 2008r2 teamed 10Gb nic Vlan 111 to Cisco nexus switch, constantly reading small amounts of data for video streaming from share on NAS head

Server 3 - 2008r2 teamed 10Gb nic Vlan 111 to Cisco nexus switch, constantly reading small amounts of data for video streaming from share on NAS head

Server 4 - 2008r2 teamed 10Gb nic Vlan111 to Cisco nexus switch,

Issue:

If on server 4 you browse to the share on NAS head and initiate heavy read and write (copy and paste 16GB data) Server 2 and 3 video stream begins to stutter (meaning they cannot get their content quickly enough.) If you initiate that copy on server 4 using terracopy there is no issue though the copy takes a lot longer.

Troubleshooting:

Initiate that same copy (windows copy and paste) on the stornext volume on server 1, no stutter issue though copy time was longer. (This removes the stornext volume and read write speeds to underlying storage as a possible bottle neck.)

During copy operation check nic, cpu and memory stats on Server 1, Server 2, Server 3 and Server 4 Nic usage is less than 12.5% during copy operation. All other stats well within limits. (This removed server hardware performance bottleneck.)

Iperf tcp load test from server4 to server 1, pushed nics to 50% usage, no stutter issue. (This removes bandwidth, load balancing or underlying network issue or bottleneck.)

On server 4 copy from the nas share to local disk (read operation) half the amount of stutter

On server 4 copy to nas share from local disk (write operation) half the amount of stutter

Using Stornext DLC (Direct Lan Client) on high demand client servers has improved the situation significantly.

Question:

Why does CIFS over DFS exhibit such poor performance and is there anything that can be done to mitigate against this.

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I'm confused. Where does DFS (Distributed File System) come in to all this? –  Ryan Ries Feb 27 '13 at 13:18
    
It's a simplistic explanation were using DFS to give us resilience over 3 NAS heads that mount SAN, we came across the (sporadic) problem so we reduced the heads to one to get a more reproducible case, it was still however configured as a one target DFS –  Paddy Carroll Feb 27 '13 at 13:30

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