HP StorageWorks 4000/6000/8000 .HP StorageWorks SAN Design Reference Guide, Pa - Page 332

Continuous Access EVA with VCS 4.x This section describes the VCS 4.x data replication specifications and the supported minimum and maximum transmission rates for qualified switch and gateway pairs. Table 161 lists the network requirements for long-distance IP gateways that work with EVA VCS 4.x. Table 161 Network requirements for long-distance IP gateways with VCS 4.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 162, Table 163, and Table 164 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 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 162 and Table 163 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. 332 SAN extension