Specifications

Fibre Channel Over SONET (FC-SONET)
47Continuous Access and Data Replication Manager SAN Extensions Reference Guide
Continuous Access EVA VCS V3.025 support
Due to changes in the firmware introduced in VCS V3.025, the minimum network
supported bandwidths for the gateways have changed. At this time, Table 21 lists
the minimum quality of service requirements for the intersite network. Table 22
lists the supported switch and gateway pairs with the minimum supported network
bandwidth and number of DR Groups.
Table 21: General intersite network requirements when using long distance
gateways
Bandwidth
1
1. Pre-existing restriction
Must be dedicated to the continuous access storage
replication function
Note: No support for dynamic pacing of the gateway
at this time.
Maximum # of DR Groups See Table 22 for specific minimum supported
bandwidth based on the average packet loss ratio and
the one-way intersite latencies
Maximum Transmission Unit
(MTU) of the IP network
Set to 1500 Bytes
Maximum Latency
1
100 mSec one way one way or 200 mSec round trip
Average Packet Loss Ratio
2
2. Packet loss ratio is an indication of the need to re-transmit data across the intersite link.
Each re-transmission delays the queue behind the current packet, increasing the time to
complete transactions in the queue.
0.2% averaged over 24 hours, not to exceed 0.5% for
more than 5 minutes within a 2 hour window
Latency Jitter
3
3. Latency jitter is the difference between the minimum and maximum values; and is a
measure of how stable or predictable the delay is in the network. The greater the jitter,
the greater the variance in the delay, which lowers the predictability of the
performance.
Not to exceed 10 mSec over 24 hours