Qsan Technology P300H61, User Manual

Page: 131 / 154

131
the source virtual disk to the target virtual disk. Next time, when the rest snapshot space
has been used over 50%, in other words, the total snapshot space has been used over
75%, the subsystem will start the replication job again.
“Restart the task an hour later if failed” setting is used when running out of snapshot
space, the replication job will stop because there is no more available snapshot space. If
this option has been check, the subsystem will automatically clear the snapshots to release
snapshot space, and the replication job will restart the task after an hour.
Caution
These two settings, “Threshold” and “Restart the task an hour later if
failed” , will take effect only when the replication job is configured to run
by schedule.
Caution
The default snapshot space allocated by the subsystem is two times the
size of source virtual disk. That is the best value of QSAN ’s suggestion. If
user sets snapshot space by manually and lower than the default value,
user should take the risk if the snapshot space is not enough and
QReplica
job will fail.
•
Best practice for the first time
It is always being a problem that to do full copy over LAN or WAN when the replication job
is executed at the first time. It may take days or weeks to replicate data from source to
target subsystem with limited network bandwidth.
QSAN provides two features to help
user to shorten the time of executing full copy.
1.
One is to skip full copy on a new, clean virtual disk. The term “clean” means that the
virtual disk has never been written data since created.
2. The other way is to use “VD Clone” , which is a local data copy function between
virtual disks to execute full copy at the first time. Then move the physical drives with
the target virtual disk to the target subsystem and turn the cloning job into replication
with differential copy afterward.