HP StorageWorks 4000/6000/8000 .HP StorageWorks SAN Design Reference Guide, Pa - Page 328

Continuous Access EVA with XCS 6.x This section describes the Continuous Access EVA XCS 6.x data replication specifications and the supported minimum and maximum transmission rates for qualified switch and gateway pairs. Table 157 lists the network requirements for long-distance gateways that work with EVA XCS 6.x. Table 157 Network requirements for long-distance IP gateways with XCS 6.x Specification IP bandwidth1 Description • Must be dedicated to the Continuous Access storage replication function. • The minimum IP bandwidth required for Continuous Access EVA with FCIP is 2 Mb/s per path, or 4 Mb/s for two paths when using one IP link. • There is no support for dynamic pacing of the gateway. Maximum number of DR groups See Table 131 for the maximum number of DR groups. See Table 158 and Table 159 for minimum supported bandwidth and resulting maximum number of DR groups based on the average packet-loss ratio and one-way inter-site latencies. MTU of the IP network Maximum latency1 Average packet-loss ratio2 1,500 bytes 100 ms IP network delay one-way or 200 ms round-trip Low-loss network: 0.0012% average over 24 hours High-loss network: 0.2% average over 24 hours; must not exceed 0.5% for more than 5 minutes in a two-hour window Latency jitter3 Must not exceed 10 ms over 24 hours 1Pre-existing restriction 2A high packet-loss ratio indicates the need to retransmit data across the inter-site link. Each retransmission delays transmissions queued behind the current packet, thus increasing the time to complete pending transactions. Unless noted otherwise, gateways listed in Table 158 and Table 159 are supported in both low-loss and high-loss networks. 3Latency jitter is the difference between the minimum and maximum values, and indicates how stable or predictable the network delay. The greater the jitter, the greater the variance in the delay, which lowers the performance predictability. NOTE: Applications typically require more than the minimum bandwidth to meet throughput requirements. To increase the maximum number of DR groups, you must increase the minimum available IP bandwidth. For example, if the maximum number of DR groups required is 10, increase the minimum available bandwidth to 10 Mb/s; for 15 DR groups, increase to 15 Mb/s; and for 128 DR groups, increase the minimum available bandwidth to 128 Mb/s. 328 SAN extension