HP StorageWorks 1606 Brocade Fabric OS Command Reference v6.3.0 (53-1001337-01 - Page 419

iodSet 2 iodSet Enables in-order delivery (IOD) with or without frame drop. Synopsis iodset iodset --enable -losslessDLS iodset --disable -losslessDLS iodset --show iodset --help Description Use this command to enforce in-order delivery of frames during a fabric topology change and to enable dynamic load sharing (DLS) without frame loss. In a stable fabric, frames are always delivered in order, even when the traffic between switches is shared among multiple paths. However, when topology changes occur in the fabric (for instance, a link goes down), traffic is rerouted around the failure and some frames might be delivered out of order. This command ensures that frames are not delivered out-of-order, even during fabric topology changes. Dynamic load sharing optimizes utilization of the interswitch links (ISLs) by rebalancing the paths going over the ISLs whenever there is a fabric event that could result in sub-optimal utilization of the ISL. The iodSet command ensures that there is a sufficient delay between the event that causes an existing path to be removed and the establishment of a new path, so that frames are delivered in order. However, this also means that frames are dropped during the delay, causing I/O failures. When used without operands, iodSet enables in-order-delivery of frames on a switch (legacy IOD behavior). Frame loss is unavoidable when a port goes down. Enabling -lossLessDLS ensures that no frames are lost when the port comes back with a new path. This feature can be enabled on a logical switch (LS), but it affects other logical switches that share the same hardware. Chassis-level permissions are required to control this feature, even though the feature is turned on only for a specific LS. For example, assume a chassis is partitioned as follows: logical switch LS1 consists of ports 1/1-5, and logical switch LS2 consists of ports 1/6 -10. Lossless DLS is enabled on logical switch LS1. Since the ports 1/0 -10 share the same chip, traffic in LS2 will also be affected whenever traffic for LS1 on ports 1/0-5 is rebalanced. The effect on LS2 depends on the configuration on LS2: • If IOD is set on LS2 (iodSet without operands), IOD is enforced on LS2, but with frame loss. • If lossless DLS is enabled on LS2, traffic pauses and resumes without frame loss. • If IOD is not set on LS2 (iodReSet onLS2), traffic pauses and resumes with frame loss. IOD is disabled by default. Use iodSet --show to display current settings. Notes Lossless DLS is supported only on the Brocade DCX, DCX-4S with 8 G blades (Condor2), and on the Brocade 5300 and 5100. All other platforms continue to enforce the legacy IOD implementation. Lossless DLS is supported only in FICON environments, and the switch must be configured with a port-based policy. Refer to aptPolicy help for more information. Lossless DLS is not supported on extended interswitch links (ISLs). Fabric OS Command Reference 389 53-1001337-01