How Replication Redundancy Works; Normal Operation - Overland Storage SnapSAN S1000 User Manual

SnapSAN S1000 User Guide
To configure the snapshot space settings of Replication, click Configuration.
There are three settings in the Replication configuration menu:
• Snapshot space – specifies the ratio of snapshot space allocated to the Source virtual
disk automatically when the snapshot space is not configured in advance. The default
ratio is 2 to 1 which means when the replication job is being created, the subsystem
will automatically use the free space of RAID group to create a snapshot space which is
double the size of the Source virtual disk.
• Threshold – monitors the utilization of snapshot space. When the used snapshot
space reaches its threshold, the subsystem will automatically take a new snapshot and
start the replication job. The purpose of the threshold is to prevent the incremental
copy from immediately failing when it runs out of snapshot space.
For example, the default threshold is set to 50%. When the snapshot space used goes
over 50%, the subsystem automatically replicates data from the Source virtual disk to
the Target virtual disk. After that, when the remaining unused snapshot space goes
over 50% (for a total snapshot space used of 75%), the subsystem automatically starts
the replication job again.
• Restart the task an hour later if failed – for use when running out of snapshot
space and the replication job has stopped due to the lack of space. If checked, the
subsystem will automatically clear older snapshots to release snapshot space, and the
replication job will restart the task after another hour has past.
IMPORTANT: The settings Threshold and Restart the task an hour later if failed take effect only
when the replication job is configured to run by schedule.
CAUTION:
size of Source virtual disk. If the user sets the snapshot space manually and at a lower value
than the default value, there is a risk that the snapshot space will not be large enough and
replication job will fail.

How Replication Redundancy Works

NOTE: Replication job failover is not supported. As long as the controller that owns the replication

Normal Operation

The replication job is running on the Controller 1 of Source subsystem. The data is replicated
from the Controller 1 of Source subsystem to the Controller 1 of the Target subsystem.
Replication only supports the MPIO policy for failover which means the data will be
transmitted through one network path at a time.
10400310-003 01/2013
The default snapshot space allocated by the subsystem is normally two times the
job is functioning, the job is only available through it.
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How Replication Redundancy Works
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