Symptoms
N/A
Cause
In general, mostly all ethernet switches are compatible with the PowerStore storage array, thus an RPQ submission is not always required for switch approval. It is important to review the switch datasheet and correlate that data with the information listed in this document.
Resolution
The recommended switch characteristics for interoperability with PowerStore iSCSI/NAS/ethernet/inter-cluster communications are, but are not limited to:
- Minimum of 9MB of shared packet buffer for 10Gbps switches
- Minimum of 32MB of shared packet buffer for 25Gbps switches
- Full-duplex IEEE 802.3x flow control
- Multi-Chassis LAG (eg. VLT, MC-LAG, or VPC) or stacking support
- IEEE 802.3ad (LACP) implementation
- IEEE 802.1ab LLDP
- IEEE 802.1Q VLAN Tagging
It is recommended that PortFast mode (immediate forwarding state) and Storm-Control (e.g. unicast) be enabled on the edge ports. Review your switch User’s Guide.
For network switch optimization, although not mandatory, it is highly recommended that the switch support a “non-blocking” architecture.
If the ethernet switch supports the recommended characteristics listed in this document, then an RPQ does not need to be submitted.
If the ethernet switch does not support the recommended characteristics, an RPQ should be submitted for further review and should include information such as Switch datasheet, average network I/O block size (i.e. 8K, 32K, 64K), number of hosts connecting to PowerStore, MTU size and port speeds (10/25Gbps) that will be configured with PowerStore.
An RPQ should be submitted for all 1Gbps switches.
Note: If the PowerStore storage array is running version PowerStoreOS v1.x, it is mandatory to submit an RPQ for any customer that enables Cisco ACI mode. In addition, an RPQ must be submitted for any switch model that implements Software Defined Networks (SDN). One example of an SDN capable switch, but not limited to, is the Juniper QFX series. Submitting an RPQ for SDN or ACI Mode switches is mandatory regardless of if the switch already meets the recommended characteristics. However, if the PowerStore storage array is running PowerStoreOS v2.0 or newer, then an RPQ is not required for SDN or ACI mode interoperability. PowerStoreOS v2.0 or newer supports SDN and ACI mode interoperability. An RPQ should still be submitted for switches that do not meet the recommended characteristics.
Additional Information
Knowledge Information:
For an ethernet switch to efficiently process data packets to/from all edge devices, there must be a sufficient amount of shared packet buffer built into the switch. Packet buffer utilization and the use of IEEE 802.3x flow control on a switch is highly dependent on the network environment. This includes, but not limited to, the number of edge devices, MTU size, I/O transfer size, link speed (10Gbps, 25Gbps), over-subscription, and switch utilization.
In a network environment where switch ports are congested, this can cause switch port packet drops, thus leading to edge device data retransmission and elevated latency. Each data center has different network requirements, thus, may or may not require the recommended shared packet buffer sizes or flow control. In larger network deployments, a switch with a larger shared packet buffer size and/or the use of flow control may be required.
A data center administrator should always monitor the switch port metrics (i.e. packet drops, throttles) for congestion and packet drops. If switch port packets drops are excessive during iSCSI/LAN traffic, then it is recommended that you contact your switch vendor to seek a resolution to improve buffer management.
Note: In general, switch port congestion and/or packet drops on a switch is not the result of a problematic storage system, but rather a non-optimal switch that is unable to process data packets fast enough in a storage network environment.