Performance Considerations - Dell PowerVault MD3620f Command Line Interface Manual

Performance Considerations

Keep these performance considerations in mind when you create replication
relationships:
• The RAID controller module owner of a primary virtual disk performs a
full synchronization in the background while processing local I/O writes to
the primary virtual disk and associated remote writes to the secondary
virtual disk. Because the full synchronization diverts RAID controller
module processing resources from I/O writes, full synchronization can have
a performance impact to the host application.
• To reduce the performance impact, you can set the synchronization
priority level to determine how the RAID controller module owner will
prioritize the full synchronization relative to other I/O activity. To set the
synchronization priority level, consider these guidelines:
– A full synchronization at the lowest synchronization priority level
takes approximately eight times as long as a full synchronization at the
highest synchronization priority level.
– A full synchronization at the low synchronization priority level takes
approximately six times as long as a full synchronization at the highest
synchronization priority level.
– A full synchronization at the medium synchronization priority level
takes approximately three-and-a-half times as long as a full
synchronization at the highest synchronization priority level.
– A full synchronization at the high synchronization priority level takes
approximately twice as long as a full synchronization at the highest
synchronization priority level.
• When the replicated virtual disk pair is in a Synchronization in Progress
state, all host write data is copied to the remote system. Both RAID
controller module I/O bandwidth and I/O latency can affect host write
performance. Host read performance is not affected by the replication
relationship.
• The time that it takes for data to be copied from the primary virtual disk to
the secondary virtual disk might impact overall performance. This impact
is primarily caused by the delay and system resource required for copying
data to the remote replication. Some delay might also occur because of the
limit to the number of simultaneous writes.
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Using the Remote Replication Premium Feature