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17 PS Series Asynchronous Replication Best Practices and Sizing Guide | BP1012
6 Test results and analysis
This section details the test results and analyzes the data to explain the effects of each parameter on PS
Series asynchronous replication.
6.1 Effect of RAID level for the primary and secondary groups
This test measured the time it took to replicate a 100 GB volume between primary and secondary sites using
the full 10 Gb bandwidth. Then, the RAID level was changed on both primary and secondary groups to
compare the effect. First, all of the arrays were set as RAID 10 with all three arrays in the primary site as a
single pool, while the single array at the secondary site was in its own pool. Then, they were reconfigured as
RAID 50 and the test was repeated.
Replication time for RAID10 and RAID50 volumes
The results (see Figure 6) showed that there was a very slight difference (less than 5 percent) for the time it
took to replicate a 100 GB volume that resided in a RAID 10 pool compared to a volume residing in a RAID 50
pool, with the RAID 10 volume being slightly faster. Because there was little difference, RAID 50 volumes was
chosen for the remainder of the test cases because it offered greater overall storage capacity in the pools.
6.2 Effect of single or multiple volumes
When a single volume is replicated, it will consume less network (WAN) bandwidth than if multiple volumes
are being replicated simultaneously. When multiple volumes are configured for replication at the same time,
the asynchronous replication process will create an iSCSI session for each volume and transmit the
replication data over the available controller ports. When there is adequate bandwidth available between
replication partners, this can allow more data to be replicated at once compared to replication of a single
volume.
This test compared the time to complete replication for a single 100 GB volume (100% changed data) and the
three 100 GB volumes (100% changed data) across different network link speeds. Figure 7 shows that at the
17.9
18.5
0
5
10
15
20
25
RAID 10 RAID 50
Minutes
RAID 10 and RAID 50 replication time
(100 GB initial replication)