Slow iSCSI when using 1 specific iSCSI target to Compellent

Question

Hello, We have an older SC 40 providing 40TB of iSCSI storage to 8 physical servers in a Dell Blade Chassis (M1000e).  When all four iSCSI targets are connected everything appears normal.  But, we can write to a Compellent volume from a local server disk at 10-20MBps (Boo!).  If we disconnect one specific iSCSI target (Controller 2 port 2) the network transfer speed immediately improves to 110-300MBps (Yay!).  MPIO is setup and appears to work normally as well. Moving data the opposite way can be transferred at 600+MBps when any/all of the iSCSI links are connected.  We do not have software support with Dell and we cannot upgrade the Compellent OS/firmware anymore. Any ideas how to troubleshoot this?      I'm not too familiar with setting up the iSCSI network or fault domains... the networking guy (who doesn't know Compellent) said it all looks normal.  There are no errors or warnings on the Compellent or on the physical server that I can see so far. SC40 ConfigModel: CT-SC040Version: 6.3.10 (for both controllers)iSCSI ports mentioned below are 10GbpsController 1 Port 1, IP=10.26.5.49 (VLAN 5) --> Physically connected to Switch A1 TE1/1/3 Port 2, IP=10.26.6.51 (VLAN 6) --> Physically connected to Switch A2 TE1/1/3 Controller 2 Port 1, IP=10.26.5.52 (VLAN 5) --> Physically connected to Switch A1 TE1/1/4 Port 2, IP=10.26.6.50 (VLAN 6) --> Physically connected to Switch A2 TE1/1/4 Fault Domain 1 10.26.5.51 (Preferred port = controller port 1) 10.26.6.52 (Preferred port = controller port 2) Blade ChassisAll servers running Windows Server 2016 Datacenter with latest OS updates, and Dell firmwares for NIC and QLogic NIC software.  2 local disks mirrored.  Each blade server has 2 10Gbps NICs to the switches mentioned below with the appropriate VLANs configured.  All blades running Failover Cluster for Hyper-V VM's, currently running about 50+ VMs.Switch A1 (10Gbps ports) interface Te1/1/3description '10_Link_to_Compellent_1-1'spanning-tree portfastmtu 9216switchport access vlan 5exit!interface Te1/1/4description '10_Link_to_Compellent_2-1'spanning-tree portfastmtu 9216switchport access vlan 5exit Switch A2 (10Gbps ports) interface Te1/1/3description '10_Link_to_Compellent_1-2'spanning-tree portfastmtu 9216switchport access vlan 6exit!interface Te1/1/4description '10_Link_to_Compellent_2-2'spanning-tree portfastmtu 9216switchport access vlan 6exit

DELL-Sam L · Accepted Answer

Hello Andrew_P76,

Looking at your configuration, the issue that I see is that your firmware on your SC040 is not compatible with server 2016. You need to be at SCOS 6.7 which is supported for 2016.

Please let us know if you have any other questions.

Andrew_P76 · Answer

Awe, sad face. I couldn't find anywhere to download the latest OS, I'm guessing because its EOL and we don't have support for it. Does that sound about right? I've emailed our sales rep too.

Thanks for the quick response.

DELL-Sam L · Answer

Hello Andrew_P76,

You need to have a support contract on your system to get the newer versions of firmware. When a Compellent system is needing a new SCOS you need to contact support so that we can do a health check of your system. Once your system passes health check then we will release the new SCOS for your system so that you can update it.

Please let us know if you have any other questions.

Compellent

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